Liquid ejecting apparatus

ABSTRACT

A liquid ejecting apparatus includes: an inflow channel to which liquid is supplied; an outflow channel communicated with a nozzle; a liquid chamber formed with a spiral flow channel having a substantially constant cross-sectional area between the inflow channel and the outflow channel and having a given volume; a volume changing portion configured to deform the liquid chamber so as to change the volume of the liquid chamber to a volume smaller than the given volume; and an ejection control unit configured to cause the liquid to be ejected from the nozzle in a pulsed manner by driving the volume changing portion in a state in which the liquid chamber is filled with the liquid.

BACKGROUND

1. Technical Field

The present invention relates to a liquid ejecting apparatus.

2. Related Art

There is developed a liquid ejecting apparatus configured to incise orexcise living tissues by pressurizing liquid such as water orphysiologic saline and ejecting the liquid toward the living tissuesfrom a nozzle that has a reduced cross-sectional area. A surgicaloperation using such a liquid ejecting apparatus enables incision orexcision of living tissues such as internal organs exclusively andselectively without damaging nerves, blood vessels or the like, andcauses less damage to peripheral tissues. Therefore, burdens on patientscan be reduced.

In addition, there is proposed a liquid ejecting apparatus which enablesincision and excision of living tissues with a small ejecting amount bycausing liquid to be ejected in a pulsed manner instead of simplycausing the liquid to be ejected continuously from a nozzle (forexample, see JP-A-2008-082202). Such a liquid ejecting apparatus isconfigured to abruptly raise the pressure in a liquid chamber that isfilled with liquid by abruptly reducing the volume of the liquidchamber. This causes the liquid to be ejected from a nozzle connected tothe liquid chamber in a pulsed manner using the increased pressure.Subsequently, the volume of the liquid chamber is restored and theliquid chamber is again filled. By repeating such actions, a pulsed jetstream is cyclically generated.

However, such a liquid ejecting apparatus configured to eject liquid ina pulsed manner suffers in that incising and excising performance tendsto deteriorate due to accumulation of air bubbles existing in the liquidor air bubbles generated from air dissolved in the liquid under certainconditions in the liquid chamber. In other words, as described above,since a pulsed jet stream is generated by pressurizing the liquid in theliquid chamber by reducing the volume of the liquid chamber, if thereexists air bubbles in the liquid chamber, the liquid cannot bepressurized sufficiently because such air bubbles are compressed whenthe volume of the liquid chamber is reduced. Therefore, the pulsedejection of liquid from the nozzle cannot be achieved, and hence theincising and excising performances are disadvantageously lowered.

SUMMARY

An advantage of some aspects of the invention is to solve at least apart of the problems described above, and the invention can beimplemented as the following forms or application examples.

Application Example 1

This application example of the invention is directed to a liquidejecting apparatus including: an inflow channel to which liquid issupplied; an outflow channel communicated with a nozzle; a liquidchamber formed with a spiral flow channel having a substantiallyconstant cross-sectional area between the inflow channel and the outflowchannel and having a given volume; a volume changing portion configuredto deform the liquid chamber so as to change the volume of the liquidchamber to a volume smaller than the given volume; and an ejectioncontrol unit configured to cause the liquid to be ejected from thenozzle in a pulsed manner by driving the volume changing portion in astate in which the liquid chamber is filled with the liquid.

In this configuration, the liquid chamber having the spiral-shaped flowchannel is formed between the inflow channel and the outflow channeland, when the volume changing portion is driven, the liquid chamber ispressed by the volume changing portion and the volume of the liquidchamber is reduced. Consequently, the liquid in the liquid chamber isquickly pressurized, and hence high-velocity ejection of pressurizedliquid from the nozzle communicating with the outflow channel of theliquid chamber is achieved.

The liquid ejecting apparatus is configured to avoid easy accumulationof air bubbles in the liquid chamber because the liquid supplied fromthe inflow channel flows toward the outflow channel along the spiralflow channel when filing the liquid chamber with liquid.

For example, when the flow of the liquid in the liquid chamber isirregular and there are variations in flow velocity, the air bubblestend to accumulate in a portion flowing at a low velocity and the liquidcannot be pressurized sufficiently by the existence of these airbubbles. Consequently, adequate ejection of the liquid cannot beachieved. Therefore, by forming the spiral flow channel having asubstantially constant cross-sectional area between the inflow channeland the outflow channel, the flow of the liquid in the liquid chamber isrestricted to a substantially constant velocity along the spiral flowchannel. Therefore, accumulation of air bubbles in a portion where theflow of liquid is slow is inhibited, and hence the air bubbles in theliquid chamber can be discharged easily from the outflow channel.Consequently, the pressure in the liquid chamber can be increasedsufficiently without being affected by the air bubbles and hence stableejection of liquid can be maintained.

Application Example 2

In the liquid ejecting apparatus of the above application example, it ispreferred that the volume changing portion includes a piezoelectricelement, the volume of the liquid chamber is reduced by an expansion ofthe piezoelectric element, and the piezoelectric element is disposed soas to press the liquid chamber in a state that the piezoelectric elementdoes not extend/expand.

Here, the piezoelectric element expands and reduces the volume of theliquid chamber when being applied with a drive voltage waveform from theejection control unit, and contracts and restores the volume of theliquid chamber to a given volume when the application of the drivevoltage waveform is released.

The piezoelectric element which reduces the volume of the liquid chamberby expanding has such property as being resistant to a force ofcompression applied from the outside, but is vulnerable to a force oftension. Therefore, when the force of tension is applied to thepiezoelectric element, the piezoelectric element may have damage.Accordingly, by providing the piezoelectric element so as to press theliquid chamber also in a state in which the piezoelectric element is notexpanded, the force in the direction of compression can be kept actingon the piezoelectric element in advance as a reaction force of thepressure applied to the liquid chamber. Consequently, when a force inthe pulling direction is applied to the piezoelectric element, the forcein the pulling direction is alleviated, and hence the probability ofoccurrence of damage of the piezoelectric element due to the action oftensile force is reduced.

Furthermore, by providing the piezoelectric element so as to keep theliquid chamber to be pressed by the piezoelectric element also in astate in which the piezoelectric element is not expanded, the pressingof the liquid chamber is immediately started when the piezoelectricelement starts to expand. Therefore, the liquid ejection is efficientlyperformed without causing any stroke loss between the expansion of thepiezoelectric element and the reduction in volume of the liquid chamber.

Application Example 3

In the liquid ejecting apparatus of the above application example, it ispreferred that the cross-sectional area of the inflow channel is smallerthan the cross-sectional area of the outflow channel, and the inflowchannel has a capillary shape.

When the volume of the liquid chamber is reduced, the liquid is urged tobe flowed out from both of the outflow channel and the inflow channel.However since the inflow channel has a cross-sectional area smaller thanthe cross-sectional area of the outflow channel and has a capillaryshape, the pressure in the liquid chamber can be increased whileinhibiting backflow of the liquid to the inflow channel, whereby anoutflow from the outflow channel having a large cross-sectional area canbe facilitated. In this configuration, the backflow can be inhibitedeven when a check valve or the like is not provided in the inflowchannel. The term “capillary shape” of the inflow channel means a thintube having a flow channel diameter on the order of 0.3 mm, which willbe described in embodiments later.

Application Example 4

In the liquid ejecting apparatus of the above application example, it ispreferred that the liquid ejecting apparatus includes an ejection unitincluding the inflow channel, the outflow channel, the liquid chamber,and the nozzle; and a volume changing unit including the volume changingportion, and the ejection unit and the volume changing unit aredetachable attachable.

The ejecting unit is an element which causes liquid such as water, saltwater, or medical solution to flow, and may come into contact with bloodor body fluid when the liquid ejecting apparatus is used as an surgicaloperation tool. Therefore, by configuring the ejecting unit to becapable of being removed from the volume changing unit as a disposableunit, higher security is ensured.

In contrast, the volume changing unit which does not come into contactwith the liquid can be used repeatedly. Since the volume changing unitis costly in comparison with the ejecting unit, the running cost can bereduced by using the volume changing unit repeatedly.

Application Example 5

In the liquid ejecting apparatus of the above application example, it ispreferred that the liquid chamber is a flexible tube wound into a spiralshape, and the tube includes an inlet port communicated with the inflowchannel and an outlet port communicated with the outflow channel.

In the configuration in which the liquid chamber is formed of the tubehaving the inlet port and the outlet port, the layout of the inflowchannel and the outflow channel or the wound shape of the tube is notrestricted. Therefore, flexibility in design of the liquid chamber isincreased, and hence simplification of the structure of the liquidejecting apparatus or miniaturization of the same is achieved.

Also, by using the tube, the cross-sectional area of the spiral flowchannel can be kept to be substantially constant easily.

Application Example 6

In the liquid ejecting apparatus of the above application example, it ispreferred that the tube includes a gap between each of adjacent turns.

The term “between each of adjacent turns” means between a first turn anda second turn, between the second turn and a third turn, and so forth.

The volume of the tube is changed by being pressed by the volumechanging portion. In this case, by the provision of the gap by an amountcorresponding to the deformation, increase in load by pressing theadjacent turns of the tube to each other is eliminated, and the pressingamount required for ejecting liquid can be ensured.

Application Example 7

In the liquid ejecting apparatus of the above application example, it ispreferred that the inlet port is arranged at an outer-peripheral-sideend of the tube wound into a spiral shape, and the outlet port isarranged at a center-side end of the tube wound into the spiral shape.

In the liquid ejecting apparatus configured in this manner, the pressingforce in the vicinity of the center of the liquid chamber tends to bestronger than the pressing force in the peripheral portion. Therefore,since the pressure directed toward the outflow channel is increased, theliquid can be pushed out strongly.

In such configuration, the inflow channel communicated with the inletport is arranged on the outer-peripheral-side end and the outflowchannel communicated with the outlet port is arranged on the center-sideend. Therefore, when operating the liquid ejecting apparatus whileholding with hand, the nozzle located on an extension of the outflowchannel can be arranged at a substantially center of the liquid ejectingapparatus, so that an advantage of easy-to-operate is achieved.

Application Example 8

In the liquid ejecting apparatus of the above application example, it ispreferred that the inlet port is arranged at the center-side end of thetube wound into the spiral shape, and the outlet port is arranged at theouter-peripheral-side end of the tube wound into the spiral shape.

As described above, when the tube is pressed by the piezoelectricelement, the pressing amount with respect to the center portion tends tobe larger than the pressing amount with respect to the outer peripheralportion. Therefore, by arranging the inlet port at the center portion,the pressure in the vicinity of the inlet port is increased. In thiscase, by employing a capillary shape for the inlet port (inflow channel)so as to have cross-sectional areas, which is smaller than that of theoutlet port (outflow channel), a backflow from the liquid chamber to theinlet port is inhibited. Therefore, the pressure in the liquid chambercan be increased, and hence a strong liquid ejection is achieved.

Application Example 9

In the liquid ejecting apparatus of the above application example, it ispreferred that the liquid chamber is partitioned into the spiral-shapedflow channel having a substantially constant cross section area by aflexible partitioning wall between the inflow channel and the outflowchannel.

When the volume changing portion is driven in a state in which in theliquid chamber is filled with the liquid supplied from the inflowchannel, the partitioning wall is deformed and hence the volume of theliquid chamber is reduced. Consequently, the liquid pressurized in theliquid chamber flows along the spiral-shaped flow channel and guided tothe outflow channel, and is ejected from the nozzle through the outflowchannel. Therefore, with the configuration in this application example,since the liquid flows at a sufficiently high flow velocity along thespiral-shaped flow channel, accumulation of air bubbles at a portion inwhich the flow of liquid is slow is inhibited, so that the air bubblesin the liquid chamber can be discharged quickly from the outflowchannel. Consequently, the pressure in the liquid chamber can beincreased sufficiently without being affected by the air bubbles andhence stable ejection of liquid can be performed.

When the volume of the liquid chamber is reduced upon driving of thevolume changing portion, the partitioning wall is deformed so as tocause the flow channel to contract toward the outflow channel.Therefore, the pressurized liquid in the liquid chamber can be movedtoward the outflow channel and ejected strongly.

Application Example 10

In the liquid ejecting apparatus of the above application example, it ispreferred that the partitioning wall extends upright from one of asurface on the side of a first direction and a surface on the side of asecond direction, the surface on the side of the first directionconstituting the liquid chamber and configured to reduce the volume ofthe liquid chamber to a volume smaller than the given volume and thesurface on the side of the second direction opposing the surface on theside of the first direction, and the partitioning wall is provided in astate in which a distal end portion opposing the surface on the seconddirection or a distal end portion opposing the first direction is notfixed.

In this configuration, when the volume of the liquid chamber is reducedupon driving of the volume changing portion, the distal end portion ofthe partitioning wall which is not fixed can be deformed so as to beinclined toward the outflow channel. Therefore, a flow of liquiddirected toward the outflow channel beyond the partitioning wall can begenerated in the interior of the liquid chamber. In this manner, sincethe liquid is collected to the outflow channel from the peripherytogether with the flow flowing across the spiral-shaped flow channel,the liquid can be ejected adequately.

Application Example 11

In the liquid ejecting apparatus of the above application example, it ispreferred that the partitioning wall extends upright from one of asurface on the side of a first direction and a surface on the side of asecond direction, the surface on the side of the first directionconstituting the liquid chamber and configured to reduce the volume ofthe liquid chamber to a volume smaller than the given volume and thesurface on the side of the second direction opposing the surface on theside of the first direction, and the portion of the partitioning wallother than an outermost peripheral side of the partitioning wall isprovided in a state in which a distal end portion opposing the surfaceon the first direction and a distal end portion opposing the seconddirection are not fixed.

The partitioning wall in this configuration may be considered to have afixed wall on the outermost peripheral side and a movable wall on theinner peripheral side. When the volume of the liquid chamber is reducedupon driving of the volume changing portion, the partitioning wall onthe inner peripheral side, which is the movable wall, is deformed so asto move toward the outflow channel, and hence the liquid in the liquidchamber can be moved from the inflow channel toward the outflow channelof the liquid chamber.

Application Example 12

In the liquid ejecting apparatus of the above application example, it ispreferred that the inflow channel is communicated with theouter-peripheral-side end of the spiral flow channel of the liquidchamber, and the outflow channel is communicated with the center-sideend of the spiral flow channel of the liquid chamber.

In this configuration, when the liquid chamber is formed into the spiralshape by the partitioning wall, in the configuration in which the distalend of the partitioning wall is fixed, the pressure is directed from theouter periphery toward the center portion, and hence the center portionof the partitioning wall in the direction of the section is deformedtoward the center where the outflow channel exists.

In the configuration in which the distal end of the partitioning wall isnot fixed, the distal end side of the partitioning wall is deformed, anda flow of liquid flowing from the outer periphery toward the centerbeyond the partitioning wall is generated. Therefore, the liquid can becollected from the outer periphery toward the outflow channel, so thatthe liquid can be ejected strongly.

When the partitioning wall on the inner peripheral side is the movablewall, the partitioning wall is deformed so as to move toward the centerportion as if winding the spring, so that the liquid can be collected tothe center portion.

Application Example 13

In the liquid ejecting apparatus of the above application example, it ispreferred that the inflow channel is communicated with the center-sideend of the spiral flow channel of the liquid chamber, and the outflowchannel is communicated with the outer-peripheral-side end of the spiralflow channel of the liquid chamber.

In this configuration, when the liquid chamber is formed into the spiralshape by the partitioning wall, in the configuration in which the distalend of the partitioning wall is fixed, the pressure is directed from thecenter portion where the inflow channel is arranged toward the outerperiphery, the center portion of the partitioning wall in the directionof the section is deformed toward the outer periphery where the outflowchannel exists. Also, in the configuration in which the distal endportion of the partitioning wall is not fixed, the distal end portion ofthe partitioning wall is deformed toward the outer periphery, and a flowof liquid flowing from the center where the inflow channel is arrangedtoward the outer periphery where the outflow channel is arranged beyondthe partitioning wall is generated. Therefore, the liquid can becollected from the periphery toward the outflow channel, so that theliquid can be ejected strongly.

When the partitioning wall on the inner peripheral side is the movablewall, the partitioning wall is deformed so as to move toward the outerperiphery as if the spring is released, so that the liquid can becollected to the outflow channel.

In addition, as described above, since the liquid is pumped from thecenter portion to the outflow channel at the outer peripheral portion,air-bubble eliminating capability is further enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is an explanatory drawing showing a principal configuration of aliquid ejecting apparatus.

FIG. 2 is an exploded view showing an assembly of a pulsation generatoraccording to a first embodiment.

FIG. 3 is an explanatory drawing showing a configuration of a liquidchamber according to the first embodiment.

FIG. 4A is an explanatory drawing partly in cross section showing thepulsation generator in a state in which a drive voltage waveform is notapplied to a piezoelectric element.

FIG. 4B is an explanatory plan view of the liquid chamber in a state inwhich the drive voltage waveform is not applied to the piezoelectricelement.

FIG. 5A is an explanatory drawing partly in cross section showing thepulsation generator in a state in which the drive voltage waveform isapplied to the piezoelectric element.

FIG. 5B is an explanatory plan view of the liquid chamber in a state inwhich the drive voltage waveform is applied to the piezoelectricelement.

FIG. 6 is an exploded view showing an assembly of part of a pulsationgenerator according to a second embodiment.

FIG. 7 is an explanatory drawing showing a configuration of a liquidchamber according to the second embodiment.

FIG. 8 is a partly cross-sectional view showing a state in which apiezoelectric element according to the second embodiment is driven topress the liquid chamber.

FIG. 9 is an explanatory drawing showing a shape of a liquid chamberaccording to a modification.

FIG. 10 is an exploded view showing an assembly of a pulsation generatoraccording to a third embodiment.

FIG. 11 is a plan view showing the shape of a flow channel formingmember according to the third embodiment.

FIG. 12A is a partly cross-sectional view showing a state in which adrive voltage waveform is not applied to the piezoelectric elementaccording to the third embodiment.

FIG. 12B is a plan view of the liquid chamber in a state in which thedrive voltage waveform is not applied to the piezoelectric elementaccording to the third embodiment.

FIG. 13A is a partly cross-sectional view showing a state in which thedrive voltage waveform is applied to the piezoelectric element accordingto the third embodiment.

FIG. 13B is a plan view of the liquid chamber in a state in which thedrive voltage waveform is applied to the piezoelectric element accordingto the third embodiment.

FIG. 14A is a partly cross-sectional view of an internal structure of apulsation generator according to a fourth embodiment in a state in whicha drive voltage waveform is not applied to the piezoelectric element.

FIG. 14B is a partly cross-sectional view of the internal structure ofthe pulsation generator according to the fourth embodiment in a state inwhich the drive voltage waveform is applied to elongate thepiezoelectric element.

FIG. 15A is a partly cross-sectional view of an internal structure of apulsation generator according to a fifth embodiment in a state in whicha drive voltage waveform is not applied to the piezoelectric element.

FIG. 15B is a partly cross-sectional view of the internal structure ofthe pulsation generator according to the fifth embodiment in a state inwhich the drive voltage waveform is applied to elongate thepiezoelectric element.

FIG. 16 is an exploded view showing an assembly of a pulsation generatoraccording to a sixth embodiment.

FIG. 17 is an explanatory drawing showing the shape of a flow channelforming member according to the sixth embodiment.

FIG. 18A is a partly cross-sectional view showing a state in which adrive voltage waveform is applied to the piezoelectric element in thesixth embodiment.

FIG. 18B is a plan view showing the shape of the flow channel formingmember in a state in which the drive voltage waveform is applied to thepiezoelectric element in the sixth embodiment.

FIG. 19A shows part of an internal structure of a pulsation generatoraccording to a seventh embodiment in a state in which a drive voltagewaveform is not applied to the piezoelectric element.

FIG. 19B shows part of the internal structure of the pulsation generatoraccording to the seventh embodiment in a state in which the drivevoltage waveform is applied to elongate the piezoelectric element.

FIG. 20A shows part of an internal structure of a pulsation generatoraccording to an eighth embodiment in a state in which a drive voltagewaveform is not applied to the piezoelectric element.

FIG. 20B shows part of the internal structure of the pulsation generatoraccording to the eighth embodiment in a state in which the drive voltagewaveform is applied to the piezoelectric element.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Referring now to drawings, embodiments of the invention will bedescribed below.

Drawings referred to in the description given below are schematicdrawings in which members may not be drawn to scale vertical orhorizontally for purposes of illustrating respective members inrecognizable sizes.

Liquid Ejecting Apparatus

First, a configuration of a liquid ejecting apparatus 10 will bedescribed.

FIG. 1 is an explanatory drawing showing a principal configuration ofthe liquid ejecting apparatus 10. The liquid ejecting apparatus 10includes a pulsation generator 100 configured to eject liquid such aswater or physiologic saline in a pulsed manner, a liquid supply unit 300configured to supply the liquid to the pulsation generator 100, a liquidcontainer 306 configured to store the liquid to be ejected, and acontrol unit 200 as an ejection controller configured to control actionsof the pulsation generator 100 and the liquid supply unit 300.

The pulsation generator 100 has a structure including a second case 106and a first case 108 mating each other and demountably fixed to eachother by screw clamping or the like. A cylindrical liquid ejecting tube104 is connected to a surface of the second case 106 opposite from amating surface with respect to the first case 108 and a nozzle 105 isprovided at a distal end of the liquid ejecting tube 104.

Provided on the mating surface between the second case 106 and the firstcase 108 is a liquid chamber 110 in which the liquid is to be filled.The liquid chamber 110 is connected to the nozzle 105 via the liquidejecting tube 104. Provided in the interior of the first case 108 is alaminated piezoelectric element 112, which enables pulsed ejection ofthe liquid in the liquid chamber 110 from the nozzle 105 by varying thevolume of the liquid chamber 110 by applying a drive voltage waveformfrom the control unit 200 to the piezoelectric element 112 to causeexpansion and contraction thereof. Detailed configurations of thepulsation generator 100 will be described later with reference to FIG.2.

The liquid supply unit 300 is connected to a liquid container 306 via afirst connecting tube 302 and configured to supply liquid drawn from theliquid container 306 to the liquid chamber 110 of the pulsationgenerator 100 via a second connecting tube 304. The liquid supply unit300 in this embodiment, not illustrated, has a configuration in whichtwo pistons slide in cylinders, and is capable of pumping the liquidstably toward the pulsation generator 100 by adequately controlling thevelocity of movement of the both pistons.

The control unit 200 controls the action of the piezoelectric element112 that is integrated in the pulsation generator 100 and controls theaction of the liquid supply unit 300. In the liquid ejecting apparatus10 according to this embodiment, the mode of ejection of the liquid fromthe nozzle 105 can be varied by changing the flow rate of the liquid tobe supplied from the liquid supply unit 300, the drive voltage waveformto be applied to the piezoelectric element 112, and the maximum voltagevalue and the frequency.

Subsequently, the configuration of the pulsation generator 100 will bedescribed with reference to representative embodiments.

First Embodiment

FIG. 2 is an exploded view showing an assembly of the pulsationgenerator 100 according to a first embodiment. The pulsation generator100 includes the second case 106 and the first case 108 mated togetherand fixed to each other by screw clamping. Therefore, the second case106 and the first case 108 are detachable. The first case 108 is formedwith a through hole 108 h penetrating through the first case 108 andhaving a circular cross-section and at a center position of a planemated with the second case 106. The piezoelectric element 112 isaccommodated in the through hole 108 h and an opening of the throughhole 108 h on the opposite side from the mating surface with respect tothe second case 106 is covered with a third case 118. The piezoelectricelement 112 is formed of a laminated piezoelectric element, which isformed by laminating a number of piezoelectric bodies into a columnshape, and an end of the piezoelectric element 112 is fixed to the thirdcase 118. A circular reinforcing plate 116 formed of a metal plate issecured to the other end of the piezoelectric element 112. In thisembodiment, a combination of the piezoelectric element 112 and thereinforcing plate 116 corresponds to a “volume changing portion” and itreduces the volume of the liquid chamber 110.

The second case 106 is formed with a circular shallow depression 106 con the mating surface with respect to the first case 108. Formed at aposition of a peripheral edge of the depression 106 c is an inflowchannel 106 a which communicates with the second connecting tube 304connected to the second case 106. Formed at a substantially center ofthe depression 106 c is an outflow channel 106 b which communicates withthe liquid ejecting tube 104.

The liquid chamber 110 (formed of a tube 120 having a circular crosssection) is arranged in the depression 106 c of the second case 106. Inthe pulsation generator 100 of this embodiment, the liquid chamber 110is formed of a metallic tube. However, the material of the tube 120 isnot specifically limited to the metal as long as it has flexibility, anda resin-made tube may also be used. Also, the cross-sectional shape ofthe tube 120 is not limited to a circular shape, as a square shape andan oval shape may also be used.

Referring now to FIG. 3, the configuration of the liquid chamber 110will be described.

FIG. 3 is an explanatory drawing showing the configuration of the liquidchamber 110 according to the first embodiment. In FIG. 3, a state of theliquid chamber 110 viewed from the side of the first case 108 is shown.As illustrated, the liquid chamber 110 is formed into a substantiallycircular shape by winding the tube 120 into a spiral shape. Apredetermined gap is formed between each of adjacent turns of the tube120.

The diameter of the outermost periphery of the spiral-shaped tube 120 isset to be smaller than the outer diameter of the circular reinforcingplate 116. Furthermore, an outer peripheral side end and a center-sideend of the tube 120 are bent toward the second case 106 (see FIG. 2). Inthis embodiment, an opening at the outer peripheral side end of thespiral-shaped tube 120 which forms the liquid chamber 110 is referred toas an “inlet port 110 a” and an opening at the center-side end thereofis referred to as an “outlet port 110 b”.

The liquid chamber 110 configured in this manner is installed in thedepression 106 c of the second case 106 in a state in which the inletport 110 a is connected to the inflow channel 106 a, and the outlet port110 b is connected to the outflow channel 106 b as shown in FIG. 2. Whenmating and securing the second case 106 and the first case 108 withscrew clamping, the surface of the tube 120 on one side comes intocontact with a depression bottom 106 d of the second case 106, and thesurface of the tube 120 on the other side comes into contact with thereinforcing plate 116, so that the tube 120 is brought into a state ofbeing sandwiched between the depression bottom 106 d and the reinforcingplate 116.

As described above, the tube 120 is in abutment with the depressionbottom 106 d of the second case 106 on one side, and is in abutment withthe reinforcing plate 116 on the other side. Although detaileddescription is given later, in the case of the pulsation generator 100in this embodiment, the thickness or the like of the reinforcing plate116 is set so that the piezoelectric element 112 keeps a state ofpressing the side surface of the tube 120 via the reinforcing plate 116even in a state in which the drive voltage waveform is not applied andhence the piezoelectric element 112 is not expanded. However, thepressing amount in this case may be smaller than a pressing amountachieved when the drive voltage waveform is applied and hence thepiezoelectric element 112 is expanded, which just brings the reinforcingplate 116 to come into contact with the tube 120 without forming a gaptherebetween.

As shown in FIG. 2, the liquid ejecting tube 104 is connected to thesecond case 106 on the surface opposite from the mating surface withrespect to the first case 108. The inner diameter of the liquid ejectingtube 104 is set to be larger than the inner diameter of the outflowchannel 106 b. Also, the nozzle 105 having a liquid ejecting opening setto have an inner diameter smaller than that of the outflow channel 106 bis fitted by insertion to the distal end of the liquid ejecting tube104. Therefore, the cross-sectional area of a flow channel for allowingpassage of liquid pressurized in the liquid chamber 110 is increased inthe liquid ejecting tube 104 after the outflow channel 106 b and thennarrowed again at the nozzle 105 at the distal end of the liquidejecting tube 104.

Here, a configuration including the first case 108, the third case 118,the piezoelectric element 112, and the reinforcing plate 116 secured toeach other is referred to as a volume changing unit 101. A configurationincluding the second case 106, the liquid ejecting tube 104 (includingthe nozzle 105), and the tube 120 are secured to each other or fixed byinsertion is referred to as an ejecting unit 102.

The volume changing unit 101 and the ejecting unit 102 are configured tobe demountably mounted by screw fixation or the like along the matingsurface between the first case 108 and the second case 106.

With the pulsation generator 100 configured as described above, pulsatedejection of the liquid from the nozzle 105 is achieved by applying thedrive voltage waveform on the piezoelectric element 112 and causingexpansion and contraction thereof. Subsequently, an action of the liquidgenerator 100 ejecting the liquid will be described.

FIGS. 4A and 4B and FIGS. 5A and 5B are explanatory drawingsschematically showing a liquid ejecting action of pulsation generator100 in the first embodiment. FIGS. 4A and 4B show a state in which thedrive voltage waveform is not applied to the piezoelectric element 112,and FIGS. 5A and 5B show a state in which the drive voltage waveform isapplied to the piezoelectric element 112.

Referring now to FIGS. 4A and 4B, a state in which the piezoelectricelement 112 is not driven will be described. FIG. 4A is a partlycross-sectional view of the pulsation generator 100, and FIG. 4B is aplan view of the liquid chamber 110. In this state, as shown in FIG. 4A,liquid to be supplied from the liquid supply unit 300 via the secondconnecting tube 304 to the pulsation generator 100 passes through theinflow channel 106 a and flows into the liquid chamber 110, and theliquid chamber 110 is filled with the liquid. An arrow in broken line inFIG. 4A shows a flow of liquid.

As show in FIG. 4B, the liquid chamber 110 is formed with a spiral flowchannel by the tube 120 wound into a spiral shape. Liquid flowing fromthe inlet port 110 a on the periphery thereof connected to the inflowchannel 106 a turns along the tube 120 and is guided to the outlet port110 b at the center connected to the outflow channel 106 b. Indicated byarrows of a broken line in FIG. 4B is the flow of the liquid. Since thecross-sectional area of the spiral flow channel of the tube 120 issubstantially constant, the liquid in the liquid chamber 110 can beflowed at a substantially constant velocity from the inlet port 110 a tothe outlet port 110 b.

As described above, since the liquid is supplied from the liquid supplyunit 300 at a constant and stabilized pressure, when the liquid chamber110 is filled with liquid, the liquid in the liquid chamber 110 ispushed out from the outlet port 110 b through the outflow channel 106 btoward the nozzle 105 even when the piezoelectric element 112 is notdriven.

Referring now to FIGS. 5A and 5B, a state in which the piezoelectricelement 112 is driven will be described. FIG. 5A is a partlycross-sectional view of the pulsation generator 100, and FIG. 5B is aplan view of the liquid chamber 110.

When the drive voltage waveform is applied to the piezoelectric element112 in a state in which the liquid chamber 110 is filled with liquid,the piezoelectric element 112 is expanded by an increased drive voltageand presses the side surface of the tube 120 toward the depressionbottom 106 d of the second case 106 via the reinforcing plate 116 asshown in FIG. 5A. Therefore, the cross section of the tube 120 isdeformed from a circular shape to an oval shape, and the volume of theliquid chamber 110 is reduced. Consequently, the liquid in the liquidchamber 110 is pressurized.

Since the diameter of the outermost periphery of the tube 120 whichforms the liquid chamber 110 is set to be smaller than the outerdiameter of the reinforcing plate 116, the entire spiral flow channel ofthe liquid chamber 110 is brought into a pressed state. The tube 120 iswound with a predetermined gap formed between each of adjacent turns.However, when the tube 120 is pressed and deformed, the tube 120 isbrought into a state of being in tight contact with each other or astate in which the gaps are reduced. The liquid pressurized in theliquid chamber 110 in this manner is ejected from the nozzle 105 via theoutflow channel 106 b connected to the outlet port 110 b and the liquidejecting tube 104 as shown by an arrow of a broken line in FIG. 5A.

Two channels, namely, the inflow channel 106 a connected to the inletport 110 a and the outflow channel 106 b connected to the outlet port110 b are connected to the liquid chamber 110. Therefore, the liquidpressurized in the liquid chamber 110 is considered to flow out not onlyto the outflow channel 106 b, but also to the inflow channel 106 a.However, transmissibility of the liquid in the flow channel isdetermined by the cross-sectional area of the flow channel, the lengthof the flow channel, or the like. For example, when a capillary shapehaving a diameter of the outlet port 110 b to be on the order of 1 mmand a diameter of the flow channel of the inlet port 110 a to be on theorder of 0.3 mm is employed, the change of the flow rate per unit timeis proportional to the cross-sectional area and is inverselyproportional to the length. Therefore, most of the liquid can flow outto the outflow channel 106 b.

In addition, since the liquid pumped from the liquid supply unit 300tries to enter the liquid chamber 110 through the inflow channel 106 a,a backflow of the liquid in the liquid chamber 110 is prevented. Fewelements resist the outflow of the liquid in the liquid chamber 110 orincrease the inertia exist in the outflow channel 106 b. Therefore, theliquid pressurized in the liquid chamber 110 exclusively flows out tothe outflow channel 106 b and is ejected from the nozzle 105 at thedistal end thereof via the liquid ejecting tube 104.

As shown in FIG. 5B, the spiral flow channel of the liquid chamber 110is formed by winding the tube 120 in a spiral shape, and the liquidpressurized in the liquid chamber 110 moves to the outlet port 110 b atthe center along the spiral-shaped tube 120. At this time, in a portionof an outermost periphery of the spiral tube 120 that is distant fromthe central outlet port 110 b, the liquid flux is small. However, theflow rate is increased as the liquid approaches the outlet port 110 band, at a portion close to the outlet port 110 b, the liquidcorresponding to the amount of reduction of volume of the liquid chamber110 moves abruptly and pushed out from the outlet port 110 b.Consequently, the liquid is ejected at a high velocity from the nozzle105 via the outflow channel 106 b and the liquid ejecting tube 104.

When the drive voltage is subsequently lowered, the piezoelectricelement 112 contracts and is restored to its original length. Then,since the pressure from the piezoelectric element 112 is weakened, thecross section of the tube 120 which forms the liquid chamber 110 isrestored from the oval to the circle by a resiliency of the tube 120,and the volume of the liquid chamber 110 is restored to its originalvolume. Consequently, the liquid supplied from the liquid supply unit300 flows along the tube 120 and fills the interior of the liquidchamber 110, so that the piezoelectric element 112 shown in FIG. 4A isrestored to a state before being driven.

Subsequently, when the piezoelectric element 112 is expanded again dueto an increase of the drive voltage, the liquid pressurized in theliquid chamber 110 is ejected from the nozzle 105 as shown in FIG. 5A.By repeating such actions, the pulsation generator 100 in the firstembodiment is capable of generating a pulsed jet stream cyclically.

As described above, the pulsation generator 100 is preferably configuredin such a manner that the pressure is applied to the side surface of thetube 120 which forms the liquid chamber 110 even in a state in which thedrive voltage waveform is not applied to the piezoelectric element 112and hence the piezoelectric element 112 is not expanded. The reason willbe described below.

The piezoelectric element 112 configured of a laminated piezoelectricelement has the property of being resistant to a force of compressionapplied from the outside, but is vulnerable to a force of tension. Then,when the piezoelectric element 112 is compressed, the piezoelectricelement 112 is subject to a force in the pulling direction due to theinertia caused by the mass of the element itself. Therefore, thepiezoelectric element 112 may have damage such as interlayer peeling orthe like. Therefore, with such a configuration in which the pressure isapplied to the side surface of the liquid chamber 110 formed of the tube120 even when the piezoelectric element 112 is contracted, a force inthe direction of compression caused by the restoration force of the tube120 is constantly applied to the piezoelectric element 112. This causesa reduction in the pulling force applied to the piezoelectric element112. Consequently, occurrence of damage of the piezoelectric element 112due to the action of the force of tension can be reduced.

According to the first embodiment described above, by forming thespiral-shaped liquid chamber 110 having a substantially constant crosssection area between the inflow channel 106 a and the outflow channel106 b, the flow of the liquid in the liquid chamber 110 is restricted toa substantially constant velocity along the spiral flow channel.Therefore, accumulation of air bubbles in a portion where the flow ofliquid is slow is inhibited, and hence the air bubbles in the liquidchamber can be discharged easily from the outflow channel 106 b.Consequently, the pressure in the liquid chamber 110 can be increasedsufficiently without being affected by the air bubbles and hence stableejection of liquid can be maintained.

Also, by keeping the liquid chamber 110 to be pressed by thepiezoelectric element 112 also in a state in which the piezoelectricelement 112 is not expanded, the force in the direction of compressioncan be kept from acting on the piezoelectric element 112 in advance as areaction force of the pressure applied to the liquid chamber 110.Accordingly, when a pulling force is applied to the piezoelectricelement 112, the pulling force is alleviated, and hence the probabilityof damage of the piezoelectric element 112 due to the action of tensileforce is reduced.

Furthermore, by keeping the liquid chamber 110 to be pressed by thepiezoelectric element 112 also in a state in which the piezoelectricelement 112 is not expanded, the volume of the liquid chamber 110 isimmediately reduced when the piezoelectric element 112 starts to expand.Therefore, the liquid ejection is efficiently performed without causingany stroke loss between the expansion of the piezoelectric element 112and the reduction in volume of the liquid chamber 110.

Also, by setting the cross-sectional area of the inflow channel 106 a tobe smaller than the cross-sectional area of the outflow channel 106 b,the pressure in the liquid chamber 110 can be increased while inhibitinga backflow of the liquid to the inflow channel 106 a, whereby an outflowfrom the outlet port 110 b having a large cross-sectional area can befacilitated. In this configuration, the backflow can be inhibited evenwhen a check valve or the like is not provided in the inflow channel 106a.

In addition, the ejecting unit 102 and the volume changing unit 101 areconfigured to be detachable with respect to each other. The ejectingunit 102 is a unit which cause liquid such as water, salt water, ormedical solution to flow, and may come into contact with blood or bodyfluid when the liquid ejecting apparatus 10 is used as a surgicaloperation tool. Therefore, by configuring the ejecting unit 102 to becapable of being removed from the volume changing unit 101 as adisposable unit, higher security is ensured.

The volume changing unit 101 which does not come into contact with theliquid can be used repeatedly. Since the volume changing unit 101 iscostly in comparison with the ejecting unit 102, the running cost can bereduced by using the volume changing unit 101 repeatedly.

The liquid chamber 110 includes a spiral flow channel formed of theflexible tube 120 wound into a spiral shape. In the configuration inwhich the liquid chamber 110 is formed of the tube 120 in this manner,the layout of the inflow channel 106 a and the outflow channel 106 b orthe wound shape of the tube 120 is not limited by the production methodor the like. Therefore, flexibility in design of the liquid chamber 110is increased, and hence simplification of the structure of the liquidejecting apparatus 10 or miniaturization of the same is achieved.

Also, by using the tube 120 as the liquid chamber 110, thecross-sectional area of the spiral flow channel can be easily keptsubstantially constant.

The tube 120 is provided with a gap between each of adjacent turns ofthe flow channel. The tube 120 is deformed by being pressed by thepiezoelectric element 112. In this case, by the provision of the gapbetween each of the adjacent turns of the flow channel, any increase inload by pressing the adjacent turns of the tube 120 to each other iseliminated, and the pressing amount required for ejecting liquid can beensured.

Also, the inlet port 110 a is arranged at the outer-peripheral-side endof the tube 120 wound in the spiral shape, and the outlet port 110 b isarranged at the center-side end of the tube 120 wound into a spiralshape. In the liquid ejecting apparatus 10 configured in this manner,the pressing force in the vicinity of the center of the liquid chamber110 tends to be stronger than the pressing force in the outer peripheralportion. Therefore, since the pressure is increased as it goes towardthe outlet port 110 b, the liquid can be pushed out strongly.

The inflow channel 106 a which is communicated with the inlet port 110 ais arranged on the outer-peripheral-side end of the liquid chamber 110,and the outflow channel 106 b which is communicated with the outlet port110 b is arranged at the center-side end. Therefore, when operating theliquid ejecting apparatus 10 while holding with the hand, the nozzle 105located on an extension of the outflow channel 106 b can be arranged ata substantially center of the liquid ejecting apparatus 10, for ease ofoperability.

Second Embodiment

Subsequently, a second embodiment will be described with reference tothe drawings. In the first embodiment described above, the inlet port110 a is arranged on the outer-peripheral-side end of the tube 120, andthe outlet port 110 b is arranged at the center-side end of the tube120. In contrast, in the second embodiment, the arrangement of the inletport 110 a and the outlet port 110 b is reversed. Therefore, the samefunctional elements as those in the first embodiment are denoted by thesame reference numerals and configurations different from the firstembodiment are mainly described.

FIG. 6 is an exploded view showing part of an assembly of the pulsationgenerator 100 according to the second embodiment. The configurations ofthe first case 108, the piezoelectric element 112, and the reinforcingplate 116 in the second embodiment are the same as those in the firstembodiment.

In contrast, the inflow channel 106 a which communicates with the secondconnecting tube 304 connected to the second case 106 is opened at thecenter position of the depression 106 c of the second case 106, and theinlet port 110 a of the liquid chamber 110 is connected thereto. Formedat a peripheral edge of the depression 106 c is the outflow channel 106b which communicates with the liquid ejecting tube 104, and the outletport 110 b is connected thereto.

The liquid chamber 110 formed of a tube 120 having a circular crosssection is arranged in the depression 106 c. In the second embodiment,since the configurations of the liquid ejecting tube 104 and the nozzle105 are the same as those in the first embodiment although the layout isdifferent, detailed description is omitted.

Subsequently, the configuration of the liquid chamber 110 according tothe second embodiment will be described.

FIG. 7 is an explanatory drawing showing the configuration of the liquidchamber 110 according to the second embodiment. In FIG. 7, a state ofthe liquid chamber 110 viewed from the side of the first case 108 isshown. As illustrated, the liquid chamber 110 is formed into asubstantially circular shape by winding the tube 120 into a spiralshape. A predetermined gap is formed between each of adjacent turns ofthe spiral tube 120.

The diameter of the outermost periphery of the spiral shaped tube 120 isset to be smaller than the outer diameter of the circular reinforcingplate 116. Furthermore, an outer-peripheral-side end and a center-sideend of the tube 120 are bent toward the second case 106 (see FIG. 6).The inlet port 110 a at the center-side end of the spiral-shaped tube120 which forms the liquid chamber 110 is connected to the inflowchannel 106 a, and the outlet port 110 b at the outer-peripheral-sideend is connected to the outflow channel 106 b.

The liquid chamber 110 configured in this manner by the tube 120 isinstalled in the depression 106 c of the second case 106. Then, as showin FIG. 6, when mating and securing the second case 106 and the firstcase 108 with screw cramping, the surface of the tube 120 on one sidecomes into contact with a depression bottom 106 d of the second case106, and the surface of the tube 120 on the other side comes intocontact with the reinforcing plate 116, so that the tube 120 is broughtinto a state of being sandwiched between the depression bottom 106 d andthe reinforcing plate 116.

FIG. 7 is a plan view of the liquid chamber 110 according to the secondembodiment. The illustrated state is a state in which liquid to besupplied from the liquid supply unit 300 via the second connecting tube304 to the pulsation generator 100 passes through the inflow channel 106a and flows into the liquid chamber 110, and the liquid chamber 110 isfilled with the liquid. The flow of the liquid is indicated by arrows ofa broken line in FIG. 7.

The liquid chamber 110 is formed with a spiral flow channel by the tube120 wound into a spiral shape. Liquid flowing from the inlet port 110 aat the center thereof connected to the inflow channel 106 a turns alongthe tube 120 and is guided to the outlet port 110 b at the peripheraledge connected to the outflow channel 106 b. Since the cross-sectionalarea of the spiral flow channel of the tube 120 is substantiallyconstant, the liquid in the liquid chamber 110 can flow at asubstantially constant velocity from the inlet port 110 a to the outletport 110 b.

As described above, since the liquid is supplied from the liquid supplyunit 300 at a constant and stabilized pressure, when the liquid chamber110 is filled with liquid, the liquid in the liquid chamber 110 ispushed out from the outlet port 110 b through the outflow channel 106 btoward the liquid ejecting tube 104 even when the piezoelectric element112 is not driven.

FIG. 8 is a partly cross-sectional view showing a state in which thepiezoelectric element 112 is driven to press the liquid chamber 110according to the second embodiment. In FIG. 8, for easiness ofunderstanding, the deformation of the reinforcing plate 116 isexaggerated.

When the drive voltage waveform is applied to the piezoelectric element112 in a state in which the liquid chamber 110 is filled with liquid,the piezoelectric element 112 is expanded by an increased drive voltageand presses the tube 120 in the same manner as the first embodiment. Thereinforcing plate 116 has the same or larger diameter as the outerdiameter of the wound tube 120, and the piezoelectric element 112 issmaller than the outer diameter of the reinforcing plate 116.

When the tube 120, the reinforcing plate 116 and the piezoelectricelement 112 are in this relation, if the tube 120 is pressed, the outerperipheral edge of the reinforcing plate 116 is warped about the centerportion where the inlet port 110 a is disposed as shown in FIG. 8.Therefore, the pressing amount against the liquid chamber 110 is largenear the center portion, and hence the change in volume is large in thisarea. In contrast, the pressing amount is small in the outer peripheralportion, and hence the change in volume of the liquid chamber 110 issmall in this area. In other words, the pressure in the liquid chamber110 seems to be higher in the center portion and be decreased as it goestoward the outer peripheral portion. Therefore, the liquid in the liquidchamber 110 is pushed strongly from the center portion toward the outerperipheral portion.

In this manner, the pressure in the vicinity of the inlet port 110 a atthe center portion is increased, and the returned pressure of the liquidin the vicinity of the inlet port 110 a is increased correspondingly.However, since the inlet port 110 a has a capillary shape having adiameter on the order of 0.3 mm, a backflow from the liquid chamber 110to the inlet port 110 a is inhibited. Therefore, the pressure in theliquid chamber 110 can be increased, and hence a strong liquid ejectionis achieved.

The spiral flow channel of the liquid chamber 110 is formed by windingthe tube 120 in a spiral shape, and the liquid pressurized in the liquidchamber 110 moves to the outlet port 110 b at the outer-peripheral-sideend along the spiral-shaped tube 120. At this time, the flow rate isincreased as the liquid approaches the outlet port 110 b and, at aportion close to the outlet port 110 b, an amount of the liquidcorresponding to the amount of reduction of volume of the liquid chamber110 moves abruptly and is pushed out from the outlet port 110 b.Consequently, the liquid is ejected at a high velocity from the nozzle105 via the outflow channel 106 b and the liquid ejecting tube 104.

When the drive voltage is lowered subsequently, the piezoelectricelement 112 contracts and is restored to its original length. Then,since the pressing force applied by the piezoelectric element 112 isweakened, the cross section of the tube 120 which forms the liquidchamber 110 is returned from the oval to the circle by a restorationforce of the tube 120, and the volume of the liquid chamber 110 isrestored to its original volume. Subsequently, when the piezoelectricelement 112 is expanded again due to an increase of the drive voltage,the liquid pressurized in the liquid chamber 110 is ejected from thenozzle 105. By repeating such actions, the pulsation generator 100 inthe second embodiment is also capable of generating a pulsed jet streamcyclically.

In the configuration according to the second embodiment, when the tube120 is pressed by the piezoelectric element 112, the pressing amount atthe center portion tends to be larger than the pressing amount of thecenter portion tends to be larger than the pressing amount of the outerperipheral portion. Therefore, by arranging the inlet port 110 a at thecenter portion, the pressure in the vicinity of the inlet port isincreased. In this case, by employing a capillary shape havingcross-sectional areas on the order of 0.3 mm (which is smaller than thatof the outlet port 110 b and the outflow channel 106 b) for the inletport 110 a and the inflow channel 106 a, a backflow from the liquidchamber 110 to the inlet port 110 a is inhibited. Therefore, thepressure in the liquid chamber 110 can be increased, and hence a strongliquid ejection is achieved.

In addition, as described above, since the liquid is pumped from thecenter portion of the liquid chamber 110 to the outflow channel 106 b atthe outer-peripheral-side end, movement of the air bubbles isfacilitated, further eliminating air bubbles.

Modification

In the first embodiment and the second embodiment described thus far,the liquid chamber 110 is formed into a substantially circular shape bythe tube 120 wound into the spiral shape. However, the shape of theliquid chamber 110 formed by the tube 120 is not limited thereto as longas the entire tube 120 can be pressed by the elongation of thepiezoelectric element 112. A modification in which the liquid chamber110 having a shape different from those in the embodiments describedabove is employed will be described below. In the description of themodification, the same components as in the first embodiment describedabove are denoted by the same reference numerals in the first embodimentdescribed above, and detailed description will be omitted.

FIG. 9 is an explanatory drawing showing the shape of the liquid chamber110 according to a modification. As illustrated, the liquid chamber 110in the modification is formed into a substantially square shape by thetube 120 having a circular cross-section with a uniform cross-sectionalarea folded in a continuous zigzag pattern. The tube 120 is not cloggedat folded portions, and is folded while maintaining its cross-sectionalarea. The inlet port 110 a and the outlet port 110 b which form bothends of the tube 120 folded into the square shape are positioned atopposing corners of the square, respectively.

The reinforcing plate 116 is formed into a square shape corresponding tothe shape of the liquid chamber 110 as described above, and the size ofthe reinforcing plate 116 is set to be larger than the outer edge of thetube 120 folded into the square shape, so that the entirety of theliquid chamber 110 can be pressed. Although not illustrated, the secondcase 106 in the modification is formed with a square shallow depression106 c on the mating surface with respect to the first case 108, and theinflow channel 106 a is opened at a corner of the depression 106 c, andthe outflow channel 106 b is formed at an opposed corner.

In the liquid ejecting apparatus 10 in the modification as describedabove, in the same manner as the embodiments described above, when thepiezoelectric element 112 is elongated, the side surface of the tube 120which forms the liquid chamber 110 is pressed via the reinforcing plate116. At this time, the cross-sectional shape of the tube 120 isdeformed, and hence the volume of the liquid chamber 110 is reduced.Consequently, the liquid pressurized in the liquid chamber 110 can beejected from the nozzle 105 in a pulsed manner. The liquid flowed fromthe inlet port 110 a to the liquid chamber 110 flows along the foldedtube 120 to the outlet port 110 b, so that the flow of liquid in theliquid chamber 110 is restricted to a uniform flow. Therefore,accumulation of air bubbles at a portion in which the flow of liquid isslow is avoided, and the air bubbles in the liquid chamber 110 can bedischarged quickly.

As is clear from the description above, the shape of the tube 120 whichforms the liquid chamber 110 is not limited as long as it can be pressedby the elongation of the piezoelectric element 112, and the arrangementof the inlet port 110 a and the outlet port 110 b can also be set so asto be aligned with the inflow channel 106 a and the outflow channel 106b provided in the second case 106. In this manner, since the flexibilityof arrangement of the inlet port 110 a and the outlet port 110 b, andhence of the inflow channel 106 a and the outflow channel 106 b isincreased, and hence simplification of the structure of the pulsationgenerator 100 or miniaturization of the same is achieved.

Although the liquid ejecting apparatus 10 in the invention has beendescribed in conjunction with the first embodiment, the secondembodiment, and the modification, the invention is not limited to theseembodiments and may be implemented in various modes without departingthe range of the gist of the invention.

For example, it is also possible to form portions where the tube 120 isturned and portions where the tube 120 is bent between the inlet port110 a and the outlet port 110 b by combining the above-described firstembodiment or the second embodiment with the modification. In this caseas well, the similar effect as the embodiments and the modificationdescribed above may be obtained.

In the first embodiment, the second embodiment and the modificationdescribed above, the inlet port 110 a and the outlet port 110 b of theliquid chamber 110 formed of the tube 120 are connected to the inflowchannel 106 a and the outflow channel 106 b formed in the depression 106c of the second case 106 respectively. However, the end portion on theside of the inlet port 110 a of the liquid chamber 110 may be formedintegrally of the inflow channel 106 a and the tube 120.

It is also possible to extend the end portion of the tube 120 on theside of the outlet port 110 b to form the outflow channel 106 b and theliquid ejecting tube 104 integrally, and then reduce the distal end ofthe liquid ejecting tube 104 to form the nozzle 105. In thisconfiguration, since the portion from the inflow channel 106 a to thenozzle 105 can be formed integrally with the tube 120, leakage of theliquid is prevented at the pulsation generator 100. In thisconfiguration, the tube 120 is preferably formed of a metal.

Third Embodiment

Subsequently, a third embodiment will be described with reference to thedrawings. While the liquid chamber 110 is formed of the tube 120 woundinto a spiral shape in the first embodiment and the second embodiment,the third embodiment is characterized in that the liquid chamber 110 isformed of a flow channel forming member 130 having a partitioning wall130 w. Common portions to the first embodiment are denoted by the samereference numerals as the first embodiment.

FIG. 10 is an exploded view showing an assembly of the pulsationgenerator 100 according to the third embodiment. FIG. 11 is a plan viewshowing the shape of the flow channel forming member 130. The first case108 is formed with a circular shallow depression 108 c at asubstantially center position of a mating surface with respect to thesecond case 106 and the depression 108 c is formed with a through hole108 h having a circular cross-section and penetrating through the firstcase 108. Then, a circular diaphragm 114 formed of a sheet metal or thelike is secured to the bottom surface of the depression 108 c so as toclose the through hole 108 h.

The piezoelectric element 112 is accommodated in the through hole 108 hclosed by the diaphragm 114 and, in addition, the opening of the throughhole 108 h is closed by the third case 118. Inserted between thepiezoelectric element 112 and the diaphragm 114 is the circularreinforcing plate 116. Then, the thickness of the reinforcing plate 116is set so that the diaphragm 114 and the reinforcing plate 116, thereinforcing plate 116 and the piezoelectric element 112, and thepiezoelectric element 112 and the third case 118 barely come intocontact with each other in a state in which the piezoelectric element112 is accommodated in the through hole 108 h of the first case 108 andthe through hole 108 h is closed by the third case 118. An end of thepiezoelectric element 112 is secured to the third case 118, and theother end of the piezoelectric element 112 is secured to the reinforcingplate 116. A surface of the reinforcing plate 116 opposite from thepiezoelectric element 112 is secured to the diaphragm 114.

On the surface of the diaphragm 114 opposing the second case 106, theflow channel forming member 130 is fitted into the depression 108 c soas to mate a supporting panel 130 b with the diaphragm 114. The flowchannel forming member 130 includes a partitioning wall 130 w on oneside of the supporting panel 130 b so as to extend upright at the sideof the first direction toward the second case 106. The supporting panel130 b is secured to the diaphragm 114 on a surface opposite from thesurface where the partitioning wall 130 w is provided so as to extendupright therefrom. The total thickness of the supporting panel 130 b andthe diaphragm 114 is determined to be the same as the depth of thedepression 108 c. Also, the flow channel forming member 130 is formed ofa flexible material so as to be deformable. The shape of thepartitioning wall 130 w of the flow channel forming member 130 will bedescribed later with reference to FIG. 11.

In contrast, the second case 106 is formed with a circular shallowdepression 106 c on the surface mating the first case 108. Thedepression 106 c is formed to have an inner diameter smaller than theouter diameter of the supporting panel 130 b of the flow channel formingmember 130 fitted to the first case 108, and to be large enough toreceive the partitioning wall 130 w extending upright from thesupporting panel 130 b. The depth of the depression 106 c is set to besubstantially the same as the height of the partitioning wall 130 w.

When the second case 106 and the first case 108 are mated and fixed toeach other by screw clamping, the liquid chamber 110 is defined by thedepression 106 c of the second case 106 and the supporting panel 130 bof the flow channel forming member 130 fitted to the side of the firstcase 108. In addition, the end of the partitioning wall 130 w of theflow channel forming member 130 on the side of a first directionopposing the second case 106 is secured to the depression bottom 106 dof the depression 106 c, and hence a spiral-shaped flow channel(partitioned by the partitioning wall 130 w) is formed in the interiorof the liquid chamber 110.

In contrast, however, a configuration in which an end of thepartitioning wall 130 w of the flow channel (forming member 130 on theside of a second direction opposing the first case 108 is secured to thediaphragm 114 provided in the first case 108 in a state in which thesupporting panel 130 b of the flow channel forming member 130) issecured to the depression bottom 106 d of the second case 106 and thesecond case 106 and the first case 108 are mated and secured to eachother by screw clamping is also applicable.

The second case 106 is formed with the inflow channel 106 a configuredto guide liquid supplied from the second connecting tube 304 connectedto the second case 106 to the liquid chamber 110, and the outflowchannel 106 b configured to guide the liquid pressurized in the liquidchamber 110 to the liquid ejecting tube 104. The inflow channel 106 a isopened at a position of the peripheral edge of the depression 106 c, andthe outflow channel 106 b is opened at the center position of thedepression 106 c.

The liquid ejecting tube 104 is connected to the front surface of thesecond case 106, and is set to have an inner diameter larger than theinner diameter of the outflow channel 106 b. Also, the nozzle 105(having a liquid ejecting opening set to have an inner diameter smallerthan that of the outflow channel 106 b) is fitted by insertion to thedistal end of the liquid ejecting tube 104. Therefore, thecross-sectional area of a flow channel for allowing passage of liquidflowed from the liquid chamber 110 is increased in the liquid ejectingtube 104 after the outflow channel 106 b and then narrowed again at thenozzle 105 at the distal end of the liquid ejecting tube 104.

It is also possible to set the inner diameter of the outflow channel 106b to be the same as the inner diameter of the liquid ejecting tube 104and connect the outlet port 110 b directly to the liquid chamber 110.

Here, a configuration including the first case 108, the third case 118,the piezoelectric element 112, the reinforcing plate 116, and thediaphragm 114 secured to each other is referred to as the volumechanging unit 101. A configuration including the second case 106, theliquid ejecting tube 104 (including the nozzle 105), and flow channelforming member 130 are secured to each other or fixed by insertion isreferred to as the ejecting unit 102.

The volume changing unit 101 and the ejecting unit 102 are configured tobe demountably mountable by screw fixation or the like on the matingsurface between the first case 108 and the second case 106.

Referring now to FIG. 11, the configuration of the flow channel formingmember 130 will be described. FIG. 11 shows a state of the flow channelforming member 130 viewed from the side of the first case 108 opposingthe second case 106. The supporting panel 130 b of the flow channelforming member 130 is formed into the same circular shape as thediaphragm 114, and is formed with the spiral-shaped partitioning wall130 w turning inward toward the center portion of the supporting panel130 b on a surface opposing the second case 106 so as to extend uprighttherefrom.

The spiral-shaped partitioning wall 130 w is formed so that theperipheral surface of the outermost turn thereof comes into contact withthe inner peripheral surface of the depression 106 c and the radialintervals of the wound partitioning wall 130 w are set to besubstantially constant in the radial direction. As described above, whenthe second case 106 and the first case 108 are mated and fixed to eachother by screw clamping, the spiral-shaped flow channel (directed towardthe center while turning inward from the peripheral edge portion) isformed by the partitioning wall 130 w in the interior of the liquidchamber 110.

The inflow channel 106 a and the outflow channel 106 b are connected tothe depression 106 c of the second case 106. Therefore, when the secondcase 106 and the first case 108 are mated and secured to each other byscrew cramping at an adequate position, the outflow channel 106 b opensat the center portion of the spiral flow channel formed in the interiorof the liquid chamber 110, and the inflow channel 106 a opens at an endportion on the side of the peripheral edge of the spiral flow channel.

With the pulsation generator 100 configured as described above, pulsatedejection of the liquid from the nozzle 105 is achieved by applying thedrive voltage waveform on the piezoelectric element 112 to causeexpansion and contraction of the piezoelectric element 112.Subsequently, an action of the pulsation generator 100 ejecting theliquid will be described.

FIGS. 12A and 12B and FIGS. 13A and 13B are explanatory drawingsschematically showing a liquid ejecting action of pulsation generator100 in the first embodiment. FIGS. 12A and 12B show a state in which thedrive voltage waveform is not applied to the piezoelectric element 112,and FIGS. 13A and 13B show a state in which the drive voltage waveformis applied to the piezoelectric element 112.

Referring now to FIGS. 12A and 12B, the state in which the piezoelectricelement 112 is not driven will be described. FIG. 12A is a partlycross-sectional view, and FIG. 12B is a plan view of the liquid chamber110. In this state, as shown in FIG. 12A, liquid (to be supplied fromthe liquid supply unit 300 via the second connecting tube 304) passesthrough the inflow channel 106 a and flows into the liquid chamber 110,and the liquid chamber 110 is filled with the liquid. The flow of theliquid is indicated by an arrow of a broken line in FIG. 12A.

The liquid chamber 110 is defined by forming the spiral flow channelpartitioning wall 130 w into a spiral shape. Liquid flowing from theinflow channel 106 a (as indicated by arrows of a broken line shown inFIG. 12B) turns along the partitioning wall 130 w and is guided to theoutflow channel 106 b. Since the cross-sectional area of the spiral flowchannel of liquid chamber 110 (defined by the partitioning wall 130 w)is substantially constant, the liquid in the liquid chamber 110 can beflowed at a substantially constant velocity from the inflow channel 106a to the outflow channel 106 b.

Since the liquid is supplied from the liquid supply unit 300 at aconstant stable pressure, when the liquid chamber 110 is filled withliquid, the liquid in the liquid chamber 110 is pushed out through theoutflow channel 106 b toward the liquid ejecting tube 104 even when thepiezoelectric element 112 is not driven.

Referring now to FIGS. 13A and 13B, a state in which the piezoelectricelement 112 is driven will be described. FIG. 13A is a partlycross-sectional view, and FIG. 13B is a plan view of the liquid chamber110. When the drive voltage waveform is applied to the piezoelectricelement 112 in a state in which the liquid chamber 110 is filled withliquid, the piezoelectric element 112 is expanded by an increased drivevoltage and presses the side surface of the diaphragm 114 and thesupporting panel 130 b of the flow channel forming member 130 toward theliquid chamber 110 via the reinforcing plate 116 as shown in FIG. 13A.Accordingly, the volume of the liquid chamber 110 is reduced.Consequently, the liquid in the liquid chamber 110 is pressurized. Theliquid pressurized in the liquid chamber 110 in this manner is ejectedin a pulsed manner from the nozzle 105 via the outflow channel 106 b andthe liquid ejecting tube 104 as shown by an arrow of a broken line inFIG. 13A.

Two channels, namely, the inflow channel 106 a and the outflow channel106 b are communicated with the liquid chamber 110. Therefore, theliquid pressurized in the liquid chamber 110 is considered to flow outnot only from the outflow channel 106 b, but also from the inflowchannel 106 a. However, since flowability of the liquid in the flowchannel is determined by the cross-sectional area of the flow channel,the length of the flow channel or the like, the liquid is allowed toflow out easier from the outflow channel 106 b than from the inflowchannel 106 a by setting the cross-sectional areas or the lengths of theinflow channel 106 a and the outflow channel 106 b adequately. Forexample, in this embodiment, the diameter of the outflow channel 106 bis on the order of 1 mm, and the inflow channel 106 a has a capillaryshape having a diameter on the order of 0.3 mm. Therefore, the backflowfrom the inflow channel 106 a is inhibited.

Since there is a flow of liquid pumped out from the liquid supply unit300 at the inflow channel 106 a which is urged to flow into the liquidchamber 110, outflow of the liquid in the liquid chamber 110 can beprevented. However, there are but few elements which resist the outflowof the liquid in the liquid chamber 110, or which increase the fluidinertia that exists in the outflow channel 106 b. Therefore, the liquidpressurized in the liquid chamber 110 exclusively flows out from theoutflow channel 106 b and is ejected from the nozzle 105 at the distalend thereof via the liquid ejecting tube 104.

The interior of the liquid chamber 110 in the third embodiment ispartitioned into a spiral shape by the partitioning wall 130 w of theflow channel forming member 130. However, when the volume of the liquidchamber 110 is reduced due to the extension of the piezoelectric element112, the liquid in the liquid chamber 110 flows not only along thespiral-shaped partitioning wall 130 w, but also toward the center of theliquid chamber 110 upon deformation of the partitioning wall 130 wtoward the outflow channel 106 b. This point will be described as apostscript below.

When considering the partitioning wall 130 w which constitutes theinnermost turn of the multiply wound spiral-shaped partitioning wall 130w as an example, since the outflow channel 106 b is opened at the centerportion of the liquid chamber 110 inside the innermost turn of thepartitioning wall 130 w. Therefore, when the volume of the liquidchamber 110 is reduced, the liquid flows out from the outflow channel106 b and hence the pressure rise in the pulsation generator 100 isinhibited.

In contrast, since the inflow channel 106 a has a capillary shape andinhibits the outflow of the liquid, the pressure rises more on theoutside of the partitioning wall 130 w than on the inside of thepartitioning wall 130 w. Since the partitioning wall 130 w is formed ofa flexible material so as to be deformable, the liquid pushes thepartitioning wall 130 w from the outside under the higher pressuretoward the inside under the lower pressure and deforms the same toreduce the pressure difference between the inside and the outside. Sincethe partitioning wall 130 w in the third embodiment extends upright fromthe supporting panel 130 b, and is secured at the distal end to thedepression bottom 106 d of the second case 106, the center portion ofthe partitioning wall 130 w is deformed so as to bend inward by beingpushed from the outside as shown in FIG. 13A.

The pressure difference between the inside and the outside of thepartitioning wall 130 w as described above is generated not only aroundthe innermost turn of the partitioning wall 130 w, but also around thesecond innermost turn of the partitioning wall 130 w due to the inwarddeformation of the innermost turn of the partitioning wall 130 w andlowering of the outside pressure. This phenomenon propagates also to thethird innermost turn of the partitioning wall 130 w in the same manner.Therefore, the spiral-shaped partitioning wall 130 w is deformed as awhole toward the center of the liquid chamber 110 so as to contract thespiral flow channel. The displacement of the partitioning wall 130 w isthe largest on the innermost turn of the partitioning wall 130 w havinga small inner diameter as shown in FIG. 13A.

In this manner, when the volume of the liquid chamber 110 is reduced dueto the elongation of the piezoelectric element 112, the center portionof the spiral-shaped partitioning wall 130 w is deformed so as to bendtoward the center of the liquid chamber 110, so that the liquid in theliquid chamber 110 is urged toward the outflow channel 106 b at thecenter of the liquid chamber 110 to move in the direction indicated byarrows of a broken line shown in FIG. 13B.

When the volume of the liquid chamber 110 is reduced by the expansion ofthe piezoelectric element 112, the liquid of an amount corresponding tothe reduced volume is collected to the outflow channel 106 b and then ispushed out therefrom, so that the liquid is ejected from the nozzle 105at the distal end of the liquid ejecting tube 104. At this time, it isalso considered that a sufficient amount of liquid cannot be collectedfrom the periphery to the outflow channel 106 b at the center by beinghindered by the spiral-shaped partitioning wall 130 w in the liquidchamber 110. However, in the pulsation generator 100 according to thethird embodiment, the amount of displacement of the liquid chamber 110due to the expansion thereof is small, and the amount of liquid ejectedby one pulse is on the order of 1/100 of the volume of the liquidchamber 110. Therefore, a sufficient amount of liquid can be collectedto the outflow channel 106 b from the periphery by a slight deformationof the partitioning wall 130 w toward the center of the liquid chamber110.

For example, when the ejecting amount V is assumed to be 1/100 of thevolume of the liquid chamber 110, and R is the inner radius of theliquid chamber 110 and H is the thickness of the liquid chamber 110,that is, the depth of the depression 106 c, the following expression isestablished.V=πR ² H/100  (1)

When it is assumed that liquid is ejected from the nozzle 105 by anamount collected to and pushed out from the outflow channel 106 b by thedisplacement of the innermost turn of the partitioning wall 130 w towardthe center of the liquid chamber 110 by a distance s, the injectionamount V corresponds to the difference between the volume V1 of theinside of the innermost turn before deformation and the volume V2 of theinside of the innermost turn after the deformation. Therefore, when r isan inner radius of the innermost turn of the spiral-shaped partitioningwall 130 w, the following expressions are established.

V 1 = π r²H V 2 = π (r − s)²H $\begin{matrix}{V = {{V\; 1} - {V\; 2}}} \\{= {\pi\; H\left\{ {r^{2} - \left( {r^{2} - {2{rs}} + s^{2}} \right)} \right\}}} \\{= {\pi\;{H\left( {{2{rs}} - s^{2}} \right)}}}\end{matrix}$

Here, if the distance s is just a slight amount of displacement, s² isnegligible. Therefore, the following approximation is established.V≈2πrsH  (2)

Then, when the inner radius r of the innermost turn of partitioning wall130 w is set to a half (½) the inner radius R of the liquid chamber 110for example, from the expressions (1) and (2), the following equationsare established.2π(R/2)sH=7πR ² H/100  (3)s=R/100  (4)

Therefore, an amount of liquid corresponding to the ejecting amount canbe collected to the outflow channel 106 b only by a slight displacementof the innermost turn of the partitioning wall 130 w toward the centerof the liquid chamber 110 in a scale of 1/100 of the inner diameter ofthe liquid chamber 110. Therefore, the spiral-shaped partitioning wall130 w in the liquid chamber 110 does not hinder the liquid ejection.

After having ejected the liquid, the piezoelectric element 112 iscontracted to its original length by the reduction of the drive voltage.Accordingly, the volume of the liquid chamber 110 is restored to itsoriginal volume. The liquid supplied from the liquid supply unit 300 tothe liquid chamber 110 flows along the partitioning wall 130 w and hencethe interior of the liquid chamber 110 is filled therewith, and thepartitioning wall 130 w in the liquid chamber 110 is restored to itsoriginal upright state. Consequently, the piezoelectric element 112shown in FIG. 12A is restored to its original state.

When the piezoelectric element 112 is expanded again due to an increaseof the drive voltage, the liquid pressurized in the liquid chamber 110is ejected from the nozzle 105 as shown in FIG. 13A. By repeating suchactions, the pulsation generator 100 in the third embodiment is alsocapable of ejecting the liquid from the nozzle 105 in a pulsed manner.

According to the third embodiment described above, the liquid chamber110 is partitioned into the spiral-shaped flow channel having asubstantially constant cross-sectional area by the deformablepartitioning wall 130 w between the inflow channel 106 a and the outflowchannel 106 b. Then, when the piezoelectric element 112 is driven in astate in which the liquid supplied from the inflow channel 106 a isfilled in the liquid chamber 110, the partitioning wall 130 w isdeformed and hence the volume of the liquid chamber 110 is reduced, theliquid pressurized in the liquid chamber 110 flows along thespiral-shaped flow channel and is guided to the outflow channel 106 b,and the liquid is ejected from the nozzle 105 through the outflowchannel 106 b. Therefore, since the liquid flows at a sufficiently highflow velocity along the spiral flow channel, accumulation of air bubblesat a portion in which the flow of liquid is slow is inhibited, so thatthe air bubbles in the liquid chamber 110 can be discharged quickly fromthe outflow channel 106 b. Consequently, the pressure in the liquidchamber 110 can be increased sufficiently without being affected by theair bubbles and hence stable ejection of liquid can be performed.

The partitioning wall 130 w which defines the spiral flow channel in theinterior of the liquid chamber 110 is formed of a flexible material andhence is deformable, when the volume of the liquid chamber 110 isreduced by the expansion of the piezoelectric element 112, the centerportion of the spiral-shaped partitioning wall 130 w is deformed so asto be bent toward the center of the liquid chamber 110. Accordingly, thepressurized liquid in the liquid chamber 110 can move toward the centerof the liquid chamber 110. Therefore, a flow of the liquid directedtoward the outflow channel 106 b opened at the center is generatedinside the innermost turn of the spiral-shaped partitioning wall 130 w,and hence the liquid is collected to the outflow channel 106 b from theperiphery. In this manner, in the liquid ejecting apparatus 10 in thisembodiment, even though the partitioning wall 130 w is provided insidethe liquid chamber 110, ejection of the liquid is not hindered by thepartitioning wall 130 w, and hence the liquid can be ejected strongly.

Fourth Embodiment

In addition to the pulsation generator 100 according to the thirdembodiment described above, an embodiment in which the technical thoughtin the third embodiment is developed may be realized. Such otherembodiments will be described below. In the description of theseembodiments, the same components as the third embodiment are denoted bythe same reference numerals as the third embodiment, and detaileddescription of the common portions will be omitted.

FIG. 14A is an explanatory drawing of an internal structure of apulsation generator 100 according to a fourth embodiment in a state inwhich a drive voltage waveform is not applied to the piezoelectricelement 112. FIG. 14B is an explanatory drawing of the internalstructure of the pulsation generator 100 according to the fourthembodiment in a state in which the drive voltage waveform is applied toelongate the piezoelectric element 112. In the third embodimentdescribed above, the partitioning wall 130 w of the flow channel formingmember 130 extends upright from the supporting panel 130 b, and thedistal end thereof is secured to the depression bottom 106 d of thesecond case 106. However, in the fourth embodiment, the distal end ofthe partitioning wall 130 w is not secured to the depression bottom 106d of the second case 106.

As shown in FIG. 14A, the flow channel forming member 130 is providedwith the spiral-shaped partitioning wall 130 w so as to extend uprightfrom the supporting panel 130 b. Formed in the interior of the liquidchamber 110 is a spiral flow channel partitioned by the partitioningwall 130 w. However, in the fourth embodiment, unlike the thirdembodiment described above, the end portion of the partitioning wall 130w on the side of the first direction opposing the second case 106 is notsecured to the depression bottom 106 d of the second case 106, and asmall gap is provided between the distal end portion of the partitioningwall 130 w and the depression bottom 106 d.

In the pulsation generator 100 according to the fourth embodiment aswell, in the same manner as the third embodiment, the liquid flowingfrom the inflow channel 106 a opening on the peripheral edge portion ofthe liquid chamber 110 flows to the outflow channel 106 b at the centerwhile turning along the partitioning wall 130 w, whereby the liquidchamber 110 is filled with the liquid. Since the gap between the distalend of the partitioning wall 130 w and the depression bottom 106 d isvery small, the liquid flowed into the liquid chamber 110 is exclusivelyflows along the spiral flow channel.

When the piezoelectric element 112 is expanded by an application of adrive voltage waveform in a state in which the liquid chamber 110 isfilled with the liquid in this manner, the volume of the liquid chamber110 is reduced, and the liquid in the liquid chamber 110 is pressurized.At this time, since a pressure difference is generated between theinside and the outside of the partitioning wall 130 w, the partitioningwall 130 w is pressed from the outside with a higher pressure to theinside with a lower pressure and hence is deformed. In the pulsationgenerator 100 according to the fourth embodiment, since the distal endof the partitioning wall 130 w is not secured to the depression bottom106 d of the second case 106, the distal end side of the partitioningwall 130 w is deformed so as to incline toward the center of the liquidchamber 110 as shown in FIG. 14B.

In this manner, when the distal end side of the partitioning wall 130 wis inclined toward the center of the liquid chamber 110, the liquid onthe outside of the partitioning wall 130 w flows into the inside beyondthe partitioning wall 130 w. Therefore, a flow of the liquid flowingtoward the outflow channel 106 b at the center across the spiral flowchannel is generated in the interior of the liquid chamber 110.

As described thus far, in the pulsation generator 100 according to thefourth embodiment, the distal end of the partitioning wall 130 w is notsecured to the depression bottom 106 d of the second case 106. However,when the liquid chamber 110 is filled with the liquid, the flow of theliquid in the liquid chamber 110 can be restricted to a constant flowvelocity along the spiral flow channel formed by the partitioning wall130 w in the same manner as the third embodiment described above.Therefore, accumulation of air bubbles at a portion in which the flow ofliquid is slow is avoided, and the air bubbles in the liquid chamber 110can be discharged quickly.

Also, when the piezoelectric element 112 is expanded and the volume ofthe liquid chamber 110 is reduced, the distal end of the partitioningwall 130 w which is not secured to the depression bottom 106 d of thesecond case 106 falls toward the center of the liquid chamber 110,whereby the liquid flowing toward the outflow channel 106 b at thecenter beyond the partitioning wall 130 w is generated in the interiorof the liquid chamber 110. In this manner, since the liquid is collectedto the outflow channel 106 b at the center from the periphery togetherwith the flow flowing across the spiral flow channel, the liquid can beejected adequately.

Fifth Embodiment

Subsequently, the pulsation generator 100 according to a fifthembodiment will be described. In the third embodiment and the fourthembodiment, the partitioning wall 130 w of the flow channel formingmember 130 is provided so as to extend upright from the supporting panel130 b. The fifth embodiment is characterized in that the partitioningwall 130 w on the inner peripheral side of the spiral shape is notprovided so as to extend upright from the supporting panel 130 b.

FIG. 15A is an explanatory drawing showing an internal structure of thepulsation generator 100 according to the fifth embodiment in a state inwhich a drive voltage waveform is not applied to the piezoelectricelement 112. FIG. 15B is an explanatory drawing showing the internalstructure of the pulsation generator 100 according to the fifthembodiment in a state in which the drive voltage waveform is applied tothe piezoelectric element 112 and hence the piezoelectric element 112 isexpanded. In the pulsation generator 100 according to the fifthembodiment, the spiral flow channel divided by the spiral-shapedpartitioning wall 130 w is formed in the interior of the liquid chamber110 in the same manner as the third embodiment and the fourth embodimentdescribed above.

The partitioning wall 130 w is not secured to the depression bottom 106d of the second case 106, and a small gap is provided with respect tothe depression bottom 106 d. The partitioning wall 130 w does not extendentirely upright from the supporting panel 130 b. Only a portion of themultiply wound spiral partitioning wall 130 w which constitutes theoutermost tern extends upright from the supporting panel 130 b, and theremaining portion does not extend upright from the supporting panel 130b and has a small gap therefrom although having a continuous spiralshape.

In the pulsation generator 100 according to the fifth embodimentconfigured in this manner as well, when the liquid chamber 110 is filledwith the liquid, the flow of the liquid in the liquid chamber 110 isrestricted to a constant flow velocity along the spiral flow channelformed by the partitioning wall 130 w in the same manner as the thirdand fourth embodiments, the air bubbles in the liquid chamber 110 can bedischarged quickly.

In contrast, as shown in FIG. 15B, when the volume of the liquid chamber110 is reduced by the expansion of the piezoelectric element 112 andhence the pressure difference between the inside and the outside of thepartitioning wall 130 w occurs, the partitioning wall 130 w is pressedfrom the outside with a higher pressure toward the inside with a lowerpressure. At this time, the portion of the spiral-shaped partitioningwall 130 w (which is not fixed to the supporting panel 130 b) is movedtoward the center of the liquid chamber 110 as if a spring is wound up.Therefore, the pressurized liquid in the liquid chamber 110 is movedtoward the center of the liquid chamber 110. In addition, a flow of theliquid toward the outflow channel 106 b at the center is generated so asto intersect the spiral flow channel beyond the partitioning wall 130 wand hence the liquid is collected to the outflow channel 106 b from theperiphery, so that the liquid can be ejected strongly.

In the above-describe third, fourth and the fifth embodiments, theliquid supplied to the liquid chamber 110 is guided to the outflowchannel 106 b efficiently. Therefore, when the outflow channel 106 b isconfigured to be opened at the center position of the depression 106 cwhich constitutes the liquid chamber 110. However, the position wherethe outflow channel 106 b is opened is not limited to the centerposition of the depression 106 c as long as at least the positionalrelationship such that the outflow channel 106 b is opened at a positioncloser to the center of the depression 106 c than the inflow channel 106a is ensured.

Sixth Embodiment

Subsequently, the pulsation generator 100 according to a sixthembodiment will be described. In the third, fourth, and fifthembodiments described above, the outflow channel 106 b is opened at thecenter portion of the liquid chamber 110 formed into the spiral shapeand the inflow channel 106 a is opened at the outer peripheral edgeportion of the liquid chamber 110. In contrast, the sixth embodiment ischaracterized in that the outflow channel 106 b is opened at the outerperipheral edge portion of the liquid chamber 110 formed into the spiralshape, and the inflow channel 106 a is opened at the center portion ofthe liquid chamber 110. Therefore, in the description of the sixthembodiment, the same components as the third embodiment are denoted bythe same reference numerals as the third embodiment described above, anddetailed description of the common portions will be omitted.

FIG. 16 is an exploded view showing an assembly of the pulsationgenerator 100 according to a sixth embodiment. The pulsation generator100 is formed with a circular shallow depression 108 c at asubstantially center position of a mating surface between the first case108 and the second case 106. Furthermore, a circular diaphragm 114formed of a metal sheet or the like is secured to the bottom surface ofthe depression 108 c so as to close the through hole 108 h.

The piezoelectric element 112 is accommodated in the through hole 108 hclosed by the diaphragm 114. Inserted between the piezoelectric element112 and the diaphragm 114 is the circular reinforcing plate 116. Thethickness of the reinforcing plate 116 is set so that the diaphragm 114and the reinforcing plate 116, and the piezoelectric element 112 and thethird case 118 barely come into contact with each other. An end of thepiezoelectric element 112 is secured to the third case 118 (not shown),and the other end of the piezoelectric element 112 is secured to thereinforcing plate 116. A surface of the reinforcing plate 116 oppositefrom the piezoelectric element 112 is secured to the diaphragm 114.

On the side of the diaphragm 114 opposing the second case 106, the flowchannel forming member 130 (having the partitioning wall 130 w extendingupright from one surface of the circular supporting panel 130 b) isfitted into the depression 108 c so as to mate a supporting panel 130 bwith the diaphragm 114. A surface of the supporting panel 130 b(opposite from the surface where the partitioning wall 130 w extendsupright therefrom) is secured to the diaphragm 114. The total thicknessof the supporting panel 130 b and the diaphragm 114 is set to be thesame as the depth of the depression 108 c. The flow channel formingmember 130 is formed of a flexible material so as to be deformable. Theshape of the partitioning wall 130 w will be described later withreference to FIG. 17.

In contrast, the second case 106 is formed with a circular shallowdepression 106 c on the surface mating the first case 108. Then, whenthe second case 106 and the first case 108 are mated and fixed to eachother by screw clamping, the liquid chamber 110 is defined by thedepression 106 c of the second case 106 and the flow channel formingmember 130 provided on the side of the first case 108. In addition, thedistal end of the partitioning wall 130 w of the flow channel formingmember 130 on the side opposing the second case 106 is secured to thedepression bottom 106 d of the second case 106. Hence a spiral-shapedflow channel partitioned by the partitioning wall 130 w is formed in theinterior of the liquid chamber 110.

In contrast, however, a configuration is also applicable in which an endof the partitioning wall 130 w of the flow channel forming member 130 onthe side opposing the diaphragm 114 is secured to the diaphragm 114 in astate in which the supporting panel 130 b of the flow channel formingmember 130 is secured to the depression bottom 106 d of the second case106 and the second case 106 and the first case 108 are mated and securedto each other by screw cramping.

The inflow channel 106 a is communicated with the center portion of thespiral-shaped liquid chamber 110, and the outflow channel 106 b iscommunicated with the outer peripheral edge portion. The secondconnecting tube 304 is connected to the inflow channel 106 a, and theliquid ejecting tube 104 is connected to the outflow channel 106 b.

Referring now to FIG. 17, the configuration of the flow channel formingmember 130 according to the sixth embodiment will be described.

FIG. 17 is an explanatory drawing showing the shape of the flow channelforming member 130. FIG. 17 shows a state of the flow channel formingmember 130 viewed from the diaphragm 114 side. As illustrated, thesupporting panel 130 b of the flow channel forming member 130 is formedinto the same circular shape as the diaphragm 114, and is formed withthe spiral-shaped partitioning wall 130 w turning inward toward thecenter portion of the supporting panel 130 b on a surface opposing thesecond case 106 of the supporting panel 130 b so as to extend uprighttherefrom.

The spiral-shaped partitioning wall 130 w is formed so that part of theoutermost peripheral surface thereof comes into contact with the innerperipheral surface of the depression 106 c and the cross-sectional areaof the spiral flow channel between the inflow channel 106 a and theoutflow channel 106 b is substantially constant. When the second case106 and the first case 108 are mated and fixed to each other by screwclamping, the spiral-shaped flow channel directed toward the outerperipheral edge portion while turning inward from the center portion isdefined by the partitioning wall 130 w in the interior of the liquidchamber 110.

Also, as shown in FIG. 16, the inflow channel 106 a and the outflowchannel 106 b are communicated with the depression 106 c of the secondcase 106. Therefore, when the second case 106 and the first case 108 aremated and secured to each other by screw clamping at an adequateposition, the inflow channel 106 a opens at an end portion on side ofthe center of the spiral flow channel formed in the interior of theliquid chamber 110 and the outflow channel 106 b opens at an end portionon the side of the outer peripheral edge of the spiral flow channel.

With the pulsation generator 100 configured as described above as well,pulsated ejection of the liquid from the nozzle 105 is achieved byapplying the drive voltage waveform on the piezoelectric element 112 tocause expansion and contraction of the piezoelectric element 112.

Subsequently, a liquid ejecting action of the pulsation generator 100according to a sixth embodiment will be described. In a state in whichthe piezoelectric element 112 is not driven (in a state in which thedrive voltage waveform is not applied), as shown in FIGS. 16 and 17,liquid flows from the liquid supply unit 300 into the liquid chamber 110via the second connecting tube 304 through the inflow channel 106 a, sothat the liquid chamber 110 is filled with the liquid.

Formed in the interior of the liquid chamber 110 is a spiral flowchannel having a substantially constant cross-sectional area by beingpartitioned by the partitioning wall 130 w of the flow channel formingmember 130. The liquid flowed into the liquid chamber 110 from theinflow channel 106 a opening at the center portion thereof is guided tothe outflow channel 106 b opening at the outer peripheral edge portionof the liquid chamber 110 while turning along the partitioning wall 130w as indicated by arrows in a broken line in FIG. 17. In this manner, byrestricting the flow of the liquid along the partitioning wall 130 w,the variations in flow velocity in the liquid chamber 110 from part topart do not occur in the liquid chamber 110. Consequently, the liquidflowed into the liquid chamber 110 from the inflow channel 106 a flowsto the outflow channel 106 b at substantially constant flow velocity.

Since the liquid is supplied from the liquid supply unit 300 at asubstantially constant pressure without any interruption, when theliquid chamber 110 is filled with liquid, the liquid in the liquidchamber 110 is pushed out through the outflow channel 106 b toward theliquid ejecting tube 104 even when the piezoelectric element 112 is notdriven.

FIG. 18A is a partly cross-sectional view of the pulsation generator 100showing a state in which a drive voltage waveform is applied to thepiezoelectric element1 112 in the sixth embodiment, and FIG. 18B is aplan view of the flow channel forming member 130 in a state in which thedrive voltage waveform is applied to the piezoelectric element 112 inthe sixth embodiment. When the drive voltage waveform is applied to thepiezoelectric element 112 in a state in which the liquid chamber 110 isfilled with liquid, the piezoelectric element 112 is expanded by anincreased drive voltage and presses the diaphragm 114 and the supportingpanel 130 b of the flow channel forming member 130 toward the liquidchamber 110 via the reinforcing plate 116 as shown in FIG. 18A.Consequently, the volume of the liquid chamber 110 is reduced, and theliquid in the liquid chamber 110 is pressurized. The liquid pressurizedin the liquid chamber 110 in this manner is ejected from the nozzle 105via the outflow channel 106 b and the liquid ejecting tube 104 in apulsed manner as shown by an arrow of a broken line in FIG. 18A.

Two channels, namely, the inflow channel 106 a and the outflow channel106 b are connected to the liquid chamber 110. Therefore, the liquidpressurized in the liquid chamber 110 is considered to flow out not onlyfrom the outflow channel 106 b, but also from the inflow channel 106 a.However, since flowability of the liquid in the flow channel isdetermined by the cross-sectional area of the flow channel, the lengthof the flow channel, or the like, the liquid is allowed to flow outeasier from the outflow channel 106 b than from the inflow channel 106 aby appropriately setting the cross-sectional areas or the lengths of theinflow channel 106 a and the outflow channel 106 b. For example, in thefifth embodiment, the diameter of the outflow channel 106 b is on theorder of 1 mm, and the inflow channel 106 a has a capillary shape havinga diameter on the order of 0.3 mm. Therefore, the backflow from theinflow channel 106 a is inhibited.

Since there is a flow of liquid pumped out from the liquid supply unit300 and urged to flow into the liquid chamber 110 at the inflow channel106 a, outflow of the liquid in the liquid chamber 110 can be prevented.In contrast, few elements which resist the outflow of the liquid in theliquid chamber 110 or increase the fluid inertia exist in the outflowchannel 106 b. Therefore, the liquid pressurized in the liquid chamber110 exclusively flows out from the outflow channel 106 b and is ejectedfrom the nozzle 105 at the distal end thereof via the liquid ejectingtube 104.

The interior of the liquid chamber 110 in the sixth embodiment ispartitioned into a spiral shape by the partitioning wall 130 w of theflow channel forming member 130. However, when the volume of the liquidchamber 110 is reduced due to the extension of the piezoelectric element112, the liquid in the liquid chamber 110 flows not only along thespiral-shaped partitioning wall 130 w, but also toward the outerperipheral side of the liquid chamber 110 upon deformation of thepartitioning wall 130 w toward the outflow channel 106 b on the outerperipheral edge portion. This point will be described as a postscriptbelow.

First, when considering the partitioning wall 130 w which constitutesthe innermost part of the multiply wound spiral-shaped partitioning wall130 w, the inflow channel 106 a is opened at the center portion of theliquid chamber 110 inside the innermost part of the partitioning wall130 w. Therefore, when the volume of the liquid chamber 110 is reduced,the liquid flows out from the outflow channel 106 b and hence thepressure rise in the liquid chamber 110 is inhibited.

In contrast, since the inflow channel 106 a has a capillary shape andinhibits the outflow of the liquid, the pressure rises more on theinside of the partitioning wall 130 w than the outside of thepartitioning wall 130 w. Since the partitioning wall 130 w is formed ofa flexible material so as to be deformable, the liquid pushes thepartitioning wall 130 w from the inside under the higher pressure towardthe outside under the lower pressure and deforms the same to reduce thepressure difference between the inside and the outside. Since thepartitioning wall 130 w in the sixth embodiment extends upright from thesupporting panel 130 b, and is secured at the distal end to thedepression bottom 106 d of the second case 106, the center portion ofthe partitioning wall 130 w is deformed so as to bend outward by beingpushed from the inside as shown in FIG. 18A.

The pressure difference between the inside and the outside of thepartitioning wall 130 w is generated not only around the innermost turnof the partitioning wall 130 w, but also around the second innermostturn of the partitioning wall 130 w due to the outward deformation ofthe innermost turn of the partitioning wall 130 w and lowering of theinside pressure. This phenomenon propagates also to the third innermostturn of the partitioning wall 130 w. Therefore, the spiral-shapedpartitioning wall 130 w is deformed as a whole toward the outside of theliquid chamber 110 so as to enlarge the spiral.

When the volume of the liquid chamber 110 is reduced due to theelongation of the piezoelectric element 112, the center portion of thespiral-shaped partitioning wall 130 w is deformed so as to bend towardthe outside of the liquid chamber 110, so that the liquid in the liquidchamber 110 is urged to move from the center portion of the liquidchamber 110 toward the outflow channel 106 b of the outer peripheraledge portion as indicated by arrows of a broken line shown in FIG. 18B.

When the volume of the liquid chamber 110 is reduced by the expansion ofthe piezoelectric element 112, the liquid of an amount correspondingthereto is collected at the outflow channel 106 b and then pushed outtherefrom, so that the liquid is ejected from the nozzle 105 at thedistal end of the liquid ejecting tube 104. At this time, it is alsoconsidered that a sufficient amount of liquid cannot be collected fromthe periphery to the outflow channel 106 b at the outer peripheral edgeportion by being hindered by the spiral-shaped partitioning wall 130 win the liquid chamber 110. However, in the pulsation generator 100according to the sixth embodiment, the amount of displacement due to theexpansion of the piezoelectric element 112 is small, and the amount ofliquid ejected by one pulse (ejecting amount) is on the order of 1/100of the volume of the liquid chamber 110. Therefore, a sufficient amountof liquid can be collected to the outflow channel 106 b from the centerportion by a slight deformation of the partitioning wall 130 w towardthe center of the liquid chamber 110. This can be proved by theexpression (1) to the expression (4) described in the third embodiment.

As shown in FIG. 18A, the peripheral edge portion of the supportingpanel 130 b is fixed by being cramped between the first case 108 and thesecond case 106, and the outer diameter of the reinforcing plate 116 issmaller than the outer diameter of the supporting panel 130 b, and thecross-sectional dimension of the piezoelectric element 112 is smallerthan the outer diameter of the reinforcing plate 116. Therefore, whenthe liquid chamber 110 is pressed by the piezoelectric element 112, theouter peripheral edge is warped about the center portion where theinflow channel 106 a is arranged. Therefore, the pressing amount againstthe liquid chamber 110 is large near the center portion, and hence thechange in volume in this portion is large. In contrast, the pressingamount is small in the outer peripheral side, and hence the change involume of the liquid chamber 110 is small in this area. In other words,the pressure in the liquid chamber 110 seems to be higher in the centerportion and be decreased as it goes toward the outer peripheral portion.Therefore, the liquid in the liquid chamber 110 is pushed strongly fromthe center portion to the outer peripheral portion on the basis of thefact that the liquid is pumped at a substantially constant pressure fromthe liquid supply unit 300 to the inflow channel 106 a.

Therefore, the pressure in the vicinity of the inflow channel 106 a atthe center portion is increased, and the returned pressure of the liquidto the inlet port 110 a is increased correspondingly. However, since theinlet port 110 a has a diameter of a capillary shape, the backflow fromthe liquid chamber 110 to the inflow channel 106 a is inhibited.Therefore, the pressure in the liquid chamber 110 can be increased, andhence a strong liquid ejection is achieved.

In the sixth embodiment, the spiral flow channel is formed using theflow channel forming member 130, and the outflow channel 106 b iscommunicated with the outer peripheral edge portion of the liquidchamber 110 formed into the spiral shape and the inflow channel 106 a iscommunicated with the center portion of the liquid chamber 110. In thisconfiguration as well, the concepts of the fourth embodiment or of thefifth embodiment described above may be applied.

Seventh Embodiment

The seventh embodiment is different from the fourth embodiment in thearrangement of the inflow channel 106 a and the outflow channel 106 b,and the similar configurations as the fourth embodiment may be appliedas regards other points. Therefore, the same components as the fourthembodiment are denoted by the same reference numerals as the fourthembodiment, and detailed description of the common portions will beomitted.

FIG. 19A is an explanatory drawing of part of the internal structure ofthe pulsation generator 100 according to the seventh embodiment in astate in which a drive voltage waveform is not applied to thepiezoelectric element 112, and FIG. 19B is an explanatory drawing of theinternal structure of the pulsation generator 100 according to theseventh embodiment in a state in which the drive voltage waveform isapplied to the piezoelectric element 112.

As shown in FIG. 19A, the flow channel forming member 130 is providedwith the spiral-shaped partitioning wall 130 w so as to extend uprightfrom the supporting panel 130 b. Formed in the interior of the liquidchamber 110 is a spiral flow channel partitioned by the partitioningwall 130 w. In the seventh embodiment, the distal end of thepartitioning wall 130 w (opposing the second case 106) is not secured tothe depression bottom 106 d of the second case 106, and a small gap isprovided between the distal end of the partitioning wall 130 w and thedepression bottom 106 d. The outflow channel 106 b is opened at theouter peripheral edge portion of the liquid chamber 110 formed into thespiral shape, and the inflow channel 106 a is opened at the centerportion of the liquid chamber 110.

In the seventh embodiment in this configuration, in the same manner asthe fifth embodiment, the liquid flowed into the liquid chamber 110 fromthe inflow channel 106 a (opened at the center portion thereof) flows tothe outflow channel 106 b at the center while turning along thepartitioning wall 130 w, whereby the liquid chamber 110 is filled withthe liquid. Since the gap between the distal end of the partitioningwall 130 w and the depression bottom 106 d is very small, the liquidflowed into the liquid chamber 110 exclusively flows along the spiralflow channel.

When the piezoelectric element 112 is expanded by an application of adrive voltage waveform in a state in which the liquid chamber 110 isfilled with the liquid in this manner, the volume of the liquid chamber110 is reduced, and the liquid in the liquid chamber 110 is pressurized.At this time, since a pressure difference is generated between theinside and the outside of the partitioning wall 130 w, the partitioningwall 130 w is pressed from the inside with a higher pressure to theoutside with a lower pressure and hence is deformed. According to theseventh embodiment, since the distal end of the partitioning wall 130 wis not secured to the depression bottom 106 d of the second case 106,the distal end side of the partitioning wall 130 w is deformed so as toincline toward the outer peripheral side of the liquid chamber 110 asshow in FIG. 19B.

In this manner, when the distal end side of the partitioning wall 130 wis inclined toward the outer peripheral side of the liquid chamber 110,the liquid on the inside of the partitioning wall 130 w flows into theouter peripheral side beyond the partitioning wall 130 w. Therefore, aflow of the liquid flowing toward the outflow channel 106 b on the outerperipheral side across the spiral flow channel is generated in theinterior of the liquid chamber 110.

As described thus far, in the pulsation generator 100 according to theseventh embodiment, the distal end of the partitioning wall 130 w is notsecured to the depression bottom 106 d of the second case 106, but whenthe liquid chamber 110 is filled with the liquid, the flow of the liquidin the liquid chamber 110 can be restricted to a constant flow velocityalong the spiral flow channel formed by the partitioning wall 130 w inthe same manner as the fifth embodiment described above. Therefore,accumulation of air bubbles at a portion in which the flow of liquid isslow is avoided, and the air bubbles in the liquid chamber 110 can bedischarged quickly.

Also, when the piezoelectric element 112 is expanded and the volume ofthe liquid chamber 110 is reduced, the distal end of the partitioningwall 130 w which is not secured to the depression bottom 106 d of thesecond case 106 falls toward the outer periphery of the liquid chamber110, whereby the liquid flowing toward the outflow channel 106 b at thecenter beyond the partitioning wall 130 w is generated in the interiorof the liquid chamber 110. In this manner, since the liquid is collectedto the outflow channel 106 b at the center from the periphery togetherwith the flow flowing across the spiral flow channel, the liquid can beejected adequately.

Eighth Embodiment

Subsequently, the configuration of the pulsation generator 100 accordingto an eighth embodiment will be described.

The eighth embodiment is different from the fifth embodiment in thearrangement of the inflow channel 106 a and the outflow channel 106 b,and the similar configurations as the fifth embodiment may be applied asregards other points. Therefore, the same components as the fifthembodiment described above are denoted by the same reference numerals asthe fifth embodiment, and detailed description of the common portionswill be omitted.

FIG. 20A is an explanatory drawing of the internal structure of thepulsation generator 100 according to the eighth embodiment in a state inwhich a drive voltage waveform is not applied to the piezoelectricelement 112. FIG. 20B is an explanatory drawing of the internalstructure of the pulsation generator 100 according to the eighthembodiment in a state in which the drive voltage waveform is applied toelongate the piezoelectric element 112. As shown in FIG. 20A, in thepulsation generator 100 according to the eighth embodiment, the spiralflow channel (divided by the spiral-shaped partitioning wall 130 w) isformed in the interior of the liquid chamber 110 in the same manner asthe fifth embodiment described above.

The partitioning wall 130 w is not secured to the depression bottom 106d of the second case 106, and a small gap is provided with respect tothe depression bottom 106 d. The partitioning wall 130 w does not extendentirely upright from the supporting panel 130 b. Only a portion of themultiply wound spiral partitioning wall 130 w which constitutes theoutermost tern extends upright from the supporting panel 130 b, and theremaining inner peripheral portion does not extend upright from thesupporting panel 130 b and has a small gap therefrom although having acontinuous spiral shape.

In the eighth embodiment in this configuration, the liquid flowed intothe liquid chamber 110 from the inflow channel 106 a opened at thecenter portion thereof flows to the outflow channel 106 b at the outerperipheral edge portion while turning along the partitioning wall 130 w,whereby the liquid chamber 110 is filled with the liquid. Since the gapbetween the distal end of the partitioning wall 130 w and the depressionbottom 106 d and the gap between the distal end of the partitioning wall130 w and the supporting panel 130 b are very small, the liquid flowedinto the liquid chamber 110 exclusively flows along the spiral flowchannel.

In the pulsation generator 100 according to the eighth embodiment inthis manner as well, when the liquid chamber 110 is filled with theliquid, the flow of the liquid in the liquid chamber 110 is restrictedto a constant flow velocity along the spiral flow channel formed by thepartitioning wall 130 w, the air bubbles in the liquid chamber 110 canbe discharged quickly.

In contrast, as shown in FIG. 20B, when the volume of the liquid chamber110 is reduced by the expansion of the piezoelectric element 112 (andhence the pressure difference between the inside and the outside of thepartitioning wall 130 w occurs), the partitioning wall 130 w is pressedfrom the inside with a higher pressure toward the outside with a lowerpressure. At this time, the portion of the partitioning wall 130 w onthe inner peripheral portion which is not fixed to the depression bottom106 d and the supporting panel 130 b is moved toward the outer peripheryof the liquid chamber 110 as if a spring is released. Therefore, thepressurized liquid in the liquid chamber 110 is moved toward the outerperiphery of the liquid chamber 110. In addition, a flow of the liquidtoward the outflow channel 106 b located in the direction of the outerperiphery is generated so as to intersect the spiral flow channel beyondthe partitioning wall 130 w and hence the liquid is collected to theoutflow channel 106 b from the periphery, so that the liquid can beejected strongly.

In the sixth to eighth embodiments described above, the inflow channel106 a is arranged at the center portion of the liquid chamber 110 andthe outflow channel 106 b is arranged at the outer peripheral portion ofthe liquid chamber 110. By arranging the inflow channel 106 a and theoutflow channel 106 b in this manner, since the liquid is pumped fromthe center portion to the outflow channel on the outer peripheralportion, the capability of eliminating the air bubbles can further beenhanced.

In the third embodiment to the seventh embodiment described above, thespiral-shaped flow channel is formed by a partitioning wall 130 w in theinterior of the liquid chamber 110. However, the flow channel which isformed in the interior of the liquid chamber 110 is not specificallylimited as long as it has a shape proceeding toward the outflow channel106 b while turning from the inflow channel 106 a and, for example, amodification such as a zigzag pattern maybe added.

The liquid ejecting apparatus 10 described thus far may be utilized as asurgical operation tool configured to incise or excise living tissues byejecting liquid such as water or physiologic saline toward the livingtissues, including: medical use such as application of medical solutionto wounds or washing wounds, drawing using ink as liquid, washing ofprecise parts, or for a cooling apparatus of electronic apparatus byejecting a small amount of the liquid with a high speed.

What is claimed is:
 1. A liquid ejecting apparatus comprising: an inflowchannel to which liquid is supplied; an outflow channel communicatedwith a nozzle; a liquid chamber formed with a spiral flow channel havinga substantially constant cross-sectional area between the inflow channeland the outflow channel and having a given volume; a volume changingportion configured to deform the liquid chamber so as to change thevolume of the liquid chamber to a volume smaller than the given volume;and an ejection control unit configured to cause the liquid to beejected from the nozzle in a pulsed manner by driving the volumechanging portion in a state in which the liquid chamber is filled withthe liquid.
 2. The liquid ejecting apparatus according to claim 1,wherein the volume changing portion includes a piezoelectric element,the volume of the liquid chamber is reduced by an expansion of thepiezoelectric element, and the piezoelectric element is disposed so asto press the liquid chamber in a state that the piezoelectric elementdoes not extend/expand.
 3. The liquid ejecting apparatus according toclaim 1, wherein the cross-sectional area of the inflow channel issmaller than the cross-sectional area of the outflow channel, and theinflow channel has a capillary shape.
 4. The liquid ejecting apparatusaccording to claim 1, comprising: an ejection unit including the inflowchannel, the outflow channel, the liquid chamber, and the nozzle; and avolume changing unit including the volume changing portion, wherein theejection unit and the volume changing unit are detachable attachable. 5.The liquid ejecting apparatus according to claim 1, wherein the liquidchamber is a flexible tube wound into a spiral shape, and the tubeincludes an inlet port communicated with the inflow channel and anoutlet port communicated with the outflow channel.
 6. The liquidejecting apparatus according to claim 5, wherein the tube includes a gapbetween each of adjacent turns.
 7. The liquid ejecting apparatusaccording to claim 5, wherein the inlet port is arranged at anouter-peripheral-side end of the tube wound into a spiral shape, and theoutlet port is arranged at a center-side end of the tube wound into thespiral shape.
 8. The liquid ejecting apparatus according to claim 5,wherein the inlet port is arranged at the center-side end of the tubewound into the spiral shape, and the outlet port is arranged at theouter-peripheral-side end of the tube wound into the spiral shape. 9.The liquid ejecting apparatus according to claim 1, wherein the liquidchamber is partitioned into the spiral-shaped flow channel by a flexiblepartitioning wall between the inflow channel and the outflow channel.10. The liquid ejecting apparatus according to claim 9, wherein thepartitioning wall extends upright from one of a surface on the side of afirst direction and a surface on the side of a second direction, thesurface on the side of the first direction constituting the liquidchamber and configured to reduce the volume of the liquid chamber to avolume smaller than the given volume and the surface on the side of thesecond direction opposing the surface on the side of the firstdirection, and the partitioning wall is provided in a state in which adistal end portion of the partitioning wall opposing the surface on thesecond direction or a distal end portion of the partitioning wallopposing the first direction is not fixed.
 11. The liquid ejectingapparatus according to claim 9, wherein the partitioning wall extendsupright from one of a surface on the side of a first direction and asurface on the side of a second direction, the surface on the side ofthe first direction constituting the liquid chamber and configured toreduce the volume of the liquid chamber to a volume smaller than thegiven volume and the surface on the side of the second directionopposing the surface on the side of the first direction, and the portionof the partitioning wall other than an outermost turn of thepartitioning wall is provided in a state in which a distal end portionopposing the surface on the first direction and a distal end portionopposing the second direction are not fixed.
 12. The liquid ejectingapparatus according to claim 9, wherein the inflow channel iscommunicated with the outer-peripheral-side end of the spiral flowchannel of the liquid chamber, and the outflow channel is communicatedwith the center-side end of the spiral flow channel of the liquidchamber.
 13. The liquid ejecting apparatus according to claim 9, whereinthe inflow channel is communicated with the center-side end of thespiral flow channel of the liquid chamber, and the outflow channel iscommunicated with the outer-peripheral-side end of the spiral flowchannel of the liquid chamber.